Avoid invalid update rectangles in wxGrid::BlockToDeviceRect(...)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_2_BRANCH@7576 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/grid.cpp

@@ -8036,6 +8036,9 @@ wxRect wxGrid::BlockToDeviceRect( const wxGridCellCoords &topLeft,
     int cw, ch;
     m_gridWin->GetClientSize( &cw, &ch );
 
+    if (right < 0 || bottom < 0 || left > cw || top > ch)
+        return wxRect( 0, 0, 0, 0);
+
     rect.SetLeft( wxMax(0, left) );
     rect.SetTop( wxMax(0, top) );
     rect.SetRight( wxMin(cw, right) );