Fixed a NullReferenceException that occurs when selecting the BoundingBox item of a linked element. (#28)

Author: yk35

sources/RevitDBExplorer/Domain/DataModel/MemberAccessors/Element/Element_BoundingBox.cs

@@ -20,7 +20,10 @@ public Element_BoundingBox() : base((document, element) => element.get_BoundingB
         private static IEnumerable<SnoopableObject> Snoop(Document document, Element element)
         {
             yield return new SnoopableObject(document, null, new[] { new SnoopableObject(document, element.get_BoundingBox(null)) }) { NamePrefix = "view:" };
-            yield return new SnoopableObject(document, null, new[] { new SnoopableObject(document, element.get_BoundingBox(document.ActiveView)) }) { NamePrefix = "view:", Name = "Active view: " + document.ActiveView.Name };
+            if (document.ActiveView != null)
+            {
+                yield return new SnoopableObject(document, null, new[] { new SnoopableObject(document, element.get_BoundingBox(document.ActiveView)) }) { NamePrefix = "view:", Name = "Active view: " + document.ActiveView.Name };
+            }
 
         }
     }