Index: Ringtoets/Common/src/Ringtoets.Common.Forms/PropertyClasses/IllustrationPointProperties.cs
===================================================================
diff -u -r390c486bb4cd693ae2f2eaf82a30efcb51480048 -r244dd8357f6de439ff2364fa675a9e128da84b5c
--- Ringtoets/Common/src/Ringtoets.Common.Forms/PropertyClasses/IllustrationPointProperties.cs	(.../IllustrationPointProperties.cs)	(revision 390c486bb4cd693ae2f2eaf82a30efcb51480048)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/PropertyClasses/IllustrationPointProperties.cs	(.../IllustrationPointProperties.cs)	(revision 244dd8357f6de439ff2364fa675a9e128da84b5c)
@@ -138,7 +138,8 @@
                     }
 
                     // If type is not supported, throw exception (currently not possible, safeguard for future)
-                    throw new NotSupportedException($"IllustrationPointNode of type {nameof(FaultTreeIllustrationPoint)} is not supported. Supported types: {nameof(FaultTreeIllustrationPoint)} and {nameof(SubMechanismIllustrationPoint)}");
+                    throw new NotSupportedException($"IllustrationPointNode of type {illustrationPointNode.Data.GetType().Name} is not supported. " +
+                                                    $"Supported types: {nameof(FaultTreeIllustrationPoint)} and {nameof(SubMechanismIllustrationPoint)}");
                 }
                 return points.ToArray();
             }
Index: Ringtoets/Common/src/Ringtoets.Common.Forms/Views/GeneralResultFaultTreeIllustrationPointView.cs
===================================================================
diff -u -r9820d06750b3667c39aae2cea1262256f434db5e -r244dd8357f6de439ff2364fa675a9e128da84b5c
--- Ringtoets/Common/src/Ringtoets.Common.Forms/Views/GeneralResultFaultTreeIllustrationPointView.cs	(.../GeneralResultFaultTreeIllustrationPointView.cs)	(revision 9820d06750b3667c39aae2cea1262256f434db5e)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/Views/GeneralResultFaultTreeIllustrationPointView.cs	(.../GeneralResultFaultTreeIllustrationPointView.cs)	(revision 244dd8357f6de439ff2364fa675a9e128da84b5c)
@@ -99,6 +99,12 @@
             base.Dispose(disposing);
         }
 
+        /// <summary>
+        /// Updates the controls.
+        /// </summary>
+        /// <exception cref="NotSupportedException">Thrown when the top level fault tree illustration 
+        /// contains an illustration point that is not of type <see cref="FaultTreeIllustrationPoint"/> 
+        /// or <see cref="SubMechanismIllustrationPoint"/>.</exception>
         private void UpdateControls()
         {
             suspendAllEvents = true;
@@ -140,12 +146,14 @@
 
         private IEnumerable<IllustrationPointControlItem> GetIllustrationPointControlItems()
         {
-            if (data == null)
+            GeneralResult<TopLevelFaultTreeIllustrationPoint> generalResult = getGeneralResultFunc();
+
+            if (data == null || generalResult == null)
             {
-                return null;
+                return Enumerable.Empty<IllustrationPointControlItem>();
             }
 
-            return getGeneralResultFunc()?.TopLevelIllustrationPoints.Select(topLevelFaultTreeIllustrationPoint =>
+            return generalResult.TopLevelIllustrationPoints.Select(topLevelFaultTreeIllustrationPoint =>
             {
                 IllustrationPointBase illustrationPoint = topLevelFaultTreeIllustrationPoint.FaultTreeNodeRoot.Data;
 
@@ -157,6 +165,13 @@
             });
         }
 
+        /// <summary>
+        /// Returns the stochasts of the <paramref name="illustrationPoint"/>.
+        /// </summary>
+        /// <param name="illustrationPoint">The illustration point to get the stochasts from.</param>
+        /// <returns>The stochasts.</returns>
+        /// <exception cref="NotSupportedException">Thrown when <paramref name="illustrationPoint"/> 
+        /// is not of type <see cref="FaultTreeIllustrationPoint"/> or <see cref="SubMechanismIllustrationPoint"/>.</exception>
         private static IEnumerable<Stochast> GetStochasts(IllustrationPointBase illustrationPoint)
         {
             var faultTreeIllustrationPoint = illustrationPoint as FaultTreeIllustrationPoint;
@@ -171,7 +186,8 @@
                 return subMechanismIllustrationPoint.Stochasts;
             }
 
-            return null;
+            throw new NotSupportedException($"IllustrationPointNode of type {illustrationPoint.GetType().Name} is not supported. " +
+                                            $"Supported types: {nameof(FaultTreeIllustrationPoint)} and {nameof(SubMechanismIllustrationPoint)}");
         }
 
         private void UpdateIllustrationPointsFaultTreeControl()
@@ -191,6 +207,12 @@
             ProvideIllustrationPointSelection();
         }
 
+        /// <summary>
+        /// Sets the <see cref="Selection"/> based on the selection of the <see cref="IllustrationPointsControl"/>.
+        /// </summary>
+        /// <exception cref="NotSupportedException">Thrown when the top level fault tree illustration 
+        /// contains an illustration point that is not of type <see cref="FaultTreeIllustrationPoint"/> 
+        /// or <see cref="SubMechanismIllustrationPoint"/>.</exception>
         private void ProvideIllustrationPointSelection()
         {
             var selection = illustrationPointsControl.Selection as IllustrationPointControlItem;
Index: Ringtoets/Common/src/Ringtoets.Common.Forms/Views/IllustrationPointsFaultTreeControl.cs
===================================================================
diff -u -rd7706775b2e3f09e8a2a7f965668cc9595ec3fa8 -r244dd8357f6de439ff2364fa675a9e128da84b5c
--- Ringtoets/Common/src/Ringtoets.Common.Forms/Views/IllustrationPointsFaultTreeControl.cs	(.../IllustrationPointsFaultTreeControl.cs)	(revision d7706775b2e3f09e8a2a7f965668cc9595ec3fa8)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/Views/IllustrationPointsFaultTreeControl.cs	(.../IllustrationPointsFaultTreeControl.cs)	(revision 244dd8357f6de439ff2364fa675a9e128da84b5c)
@@ -59,11 +59,11 @@
             }
             set
             {
-                data = value;
-
                 drawnNodes.Clear();
 
-                pointedTreeGraphControl.Data = value != null
+                data = value;
+                
+                pointedTreeGraphControl.Data = data != null
                                                    ? RegisterNode(data.FaultTreeNodeRoot)
                                                    : null;
             }
Index: Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/GeneralResultFaultTreeIllustrationPointViewTest.cs
===================================================================
diff -u -r9820d06750b3667c39aae2cea1262256f434db5e -r244dd8357f6de439ff2364fa675a9e128da84b5c
--- Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/GeneralResultFaultTreeIllustrationPointViewTest.cs	(.../GeneralResultFaultTreeIllustrationPointViewTest.cs)	(revision 9820d06750b3667c39aae2cea1262256f434db5e)
+++ Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/GeneralResultFaultTreeIllustrationPointViewTest.cs	(.../GeneralResultFaultTreeIllustrationPointViewTest.cs)	(revision 244dd8357f6de439ff2364fa675a9e128da84b5c)
@@ -149,6 +149,27 @@
         }
 
         [Test]
+        public void GivenViewWithGeneralResultFuncReturningNotSupportedIllustrationPoint_WhenSettingData_ThenThrowsNotSupportedException()
+        {
+            // Given
+            var data = new TestCalculation
+            {
+                Output = new object()
+            };
+
+            using (var view = new GeneralResultFaultTreeIllustrationPointView(GetGeneralResultWithTopLevelIllustrationPointsOfNotSupportedType))
+            {
+                // When
+                TestDelegate test = () => view.Data = data;
+
+                // Then
+                var exception = Assert.Throws<NotSupportedException>(test);
+                Assert.AreEqual($"IllustrationPointNode of type {nameof(TestIllustrationPoint)} is not supported. " +
+                                $"Supported types: {nameof(FaultTreeIllustrationPoint)} and {nameof(SubMechanismIllustrationPoint)}", exception.Message);
+            }
+        }
+
+        [Test]
         public void GivenDisposedViewWithDataSetAndGeneralResultFuncReturningData_WhenDataNotifiesObserver_ThenControlsNoLongerSynced()
         {
             // Given
@@ -178,6 +199,19 @@
             }
         }
 
+        private static GeneralResult<TopLevelFaultTreeIllustrationPoint> GetGeneralResultWithTopLevelIllustrationPointsOfNotSupportedType()
+        {
+            return new GeneralResult<TopLevelFaultTreeIllustrationPoint>(WindDirectionTestFactory.CreateTestWindDirection(),
+                                                                         Enumerable.Empty<Stochast>(),
+                                                                         new[]
+                                                                         {
+                                                                             new TopLevelFaultTreeIllustrationPoint(
+                                                                                 WindDirectionTestFactory.CreateTestWindDirection(),
+                                                                                 "Closing situation 2",
+                                                                                 new IllustrationPointNode(new TestIllustrationPoint()))
+                                                                         });
+        }
+
         private static IllustrationPointsFaultTreeControl GetIllustrationPointsFaultTreeControl(GeneralResultFaultTreeIllustrationPointView view)
         {
             return TypeUtils.GetField<IllustrationPointsFaultTreeControl>(view, "illustrationPointsFaultTreeControl");
@@ -512,7 +546,7 @@
 
                 // Then
                 IllustrationPointsControl illustrationPointsControl = GetIllustrationPointsControl(view);
-                Assert.IsNull(illustrationPointsControl.Data);
+                CollectionAssert.IsEmpty(illustrationPointsControl.Data);
 
                 IllustrationPointsFaultTreeControl illustrationPointsFaultTreeControl = GetIllustrationPointsFaultTreeControl(view);
                 Assert.IsNull(illustrationPointsFaultTreeControl.Data);
@@ -522,7 +556,7 @@
         }
 
         [Test]
-        public void GivenViewWithGeneralResultFuncReturningNull_WhenSettingCalculationWithoutOutput_ThenControlsDataNull()
+        public void GivenViewWithGeneralResultFuncReturningNull_WhenSettingCalculationWithoutOutput_ThenControlsDataCleared()
         {
             // Given
             var mocks = new MockRepository();
@@ -537,7 +571,7 @@
 
                 // Then
                 IllustrationPointsControl illustrationPointsControl = GetIllustrationPointsControl(view);
-                Assert.IsNull(illustrationPointsControl.Data);
+                CollectionAssert.IsEmpty(illustrationPointsControl.Data);
 
                 IllustrationPointsFaultTreeControl illustrationPointsFaultTreeControl = GetIllustrationPointsFaultTreeControl(view);
                 Assert.IsNull(illustrationPointsFaultTreeControl.Data);
@@ -547,7 +581,7 @@
         }
 
         [Test]
-        public void GivenViewWithGeneralResultFuncReturningNull_WhenSettingCalculationWithoutGeneralResult_ThenIllustrationPointsControlDataSetNull()
+        public void GivenViewWithGeneralResultFuncReturningNull_WhenSettingCalculationWithoutGeneralResult_ThenIllustrationPointsControlDataCleared()
         {
             // Given
             var data = new TestCalculation
@@ -562,7 +596,7 @@
 
                 // Then
                 IllustrationPointsControl illustrationPointsControl = GetIllustrationPointsControl(view);
-                Assert.IsNull(illustrationPointsControl.Data);
+                CollectionAssert.IsEmpty(illustrationPointsControl.Data);
 
                 IllustrationPointsFaultTreeControl illustrationPointsFaultTreeControl = GetIllustrationPointsFaultTreeControl(view);
                 Assert.IsNull(illustrationPointsFaultTreeControl.Data);
@@ -632,7 +666,7 @@
 
                 // Precondition
                 IllustrationPointsControl illustrationPointsControl = GetIllustrationPointsControl(view);
-                Assert.IsNull(illustrationPointsControl.Data);
+                CollectionAssert.IsEmpty(illustrationPointsControl.Data);
 
                 IllustrationPointsFaultTreeControl illustrationPointsFaultTreeControl = GetIllustrationPointsFaultTreeControl(view);
                 Assert.IsNull(illustrationPointsFaultTreeControl.Data);
@@ -694,7 +728,7 @@
                 data.NotifyObservers();
 
                 // Then
-                Assert.IsNull(illustrationPointsControl.Data);
+                CollectionAssert.IsEmpty(illustrationPointsControl.Data);
                 Assert.IsNull(illustrationPointsFaultTreeControl.Data);
             }
         }