Clear attribute cache in Redimension to fix Bug 508407.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@16912 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/grid.cpp

@@ -3994,6 +3994,9 @@ bool wxGrid::Redimension( wxGridTableMessage& msg )
     int i;
     bool result = FALSE;
 
+    // Clear the attribute cache as the attribute might refer to a different
+    // cell than stored in the cache after adding/removing rows/columns.
+    ClearAttrCache();
 #if 0
     // if we were using the default widths/heights so far, we must change them
     // now