fix crash on impress quit, when custom shapes were added during editing

 - reset connection to this unoshape in sdr object so that it doesn't
   try to delete uno shape later when it might be already deleted

Change-Id: I1195bfdaccceb9d7e3e0f0a48aaacb16f7a46ced

svx/source/unodraw/unoshape.cxx

@@ -1101,8 +1101,11 @@ void SvxShape::Notify( SfxBroadcaster&, const SfxHint& rHint ) throw()
 
     if( bClearMe )
     {
-        if( !HasSdrObjectOwnership() )
+        if( !HasSdrObjectOwnership() ) {
+            if( mpObj.is() )
+                mpObj->setUnoShape( NULL );
             mpObj.reset( NULL );
+        }
         if ( !mpImpl->mbDisposing )
             dispose();
     }