Fix null dereference in 2D intersection view synchronization

In Rim2dIntersectionViewCollection::syncFromExistingIntersections the
branch reusing an existing view dereferenced the RimGridView ancestor
without a null check, while the branch creating a new view already
guarded it with "if ( view )".

Intersections created without a RimGridView ancestor (for example via
the gRPC/Python API on a detached intersection collection) have a null
ancestor, causing a crash on the cellVisibilityChanged disconnect/connect
calls. Guard these calls with the same null check used in the new-view
branch and always push the existing view back into the collection.

ApplicationLibCode/ProjectDataModel/Rim2dIntersectionViewCollection.cpp

@@ -108,9 +108,12 @@ void Rim2dIntersectionViewCollection::syncFromExistingIntersections( bool doUpda
         }
         else
         {
-            view->cellVisibilityChanged.disconnect( it->second );
+            if ( view )
+            {
+                view->cellVisibilityChanged.disconnect( it->second );
+                view->cellVisibilityChanged.connect( it->second, &Rim2dIntersectionView::onCellVisibilityChanged );
+            }
             m_intersectionViews.push_back( it->second );
-            view->cellVisibilityChanged.connect( it->second, &Rim2dIntersectionView::onCellVisibilityChanged );
         }
     }