- Prevent NPE by checking type before casting

refs 1841

org.fortiss.tooling.base.ui/trunk/src/org/fortiss/tooling/base/ui/annotation/view/AnnotationViewPartBase.java

@@ -99,7 +99,7 @@ public abstract class AnnotationViewPartBase extends ViewPart implements ISelect
 				// PlatformArchitectureDiagramEditPart
 				DiagramEditPartBase<?> diagramPart =
 						SelectionUtils.checkAndPickFirst(selection, DiagramEditPartBase.class);
-				if(diagramPart != null) {
+				if(diagramPart != null && diagramPart.getModel() instanceof IModelElement) {
 					currentlySelectedObject = (IModelElement)diagramPart.getModel();
 				}
 			}