jQuery Grid Plugin - jqGrid

When upgrading from 3.8.1 to 4.0,  I discovered a bug in the grouping code.  The project that I work on allows the user to enable/disable grouping.  If the grid is initially loaded without grouping enabled and I call jqGrid('groupingGroupBy', {...}) an error occurs in groupingGroupBy when accessing groupingView.visibilityOnNextGrouping.  I was able to fix this by modifiying groupingGroupBy so that it first checks if groupingView.visibilityOnNextGrouping is undefined and if so initialize it to an empty array.  Hopefully this fix can be integrated into a future release.