Error in SDK 4.11

[mark goldin]

I have a datagrid with custom headers and no data assigned, not sure though
if that causes the problem, but when I click on the header I am getting
this:
public function getHeaderRendererAt(columnIndex:int):IGridItemRenderer
    {
        // TODO: fix this: do the work here, rather than the layout

const view:Group = getColumnHeaderViewAtIndex(columnIndex);
        *return
GridHeaderViewLayout(view.layout).getHeaderRendererAt(columnIndex);*
    }

TypeError: Error #1009: Cannot access a property or method of a null object
reference.
at
spark.components::GridColumnHeaderGroup/getHeaderRendererAt()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/spark/src/spark/components/GridColumnHeaderGroup.as:921]
at
spark.components::GridColumnHeaderGroup/dispatchGridEvent()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/spark/src/spark/components/GridColumnHeaderGroup.as:1266]
at
spark.components::GridColumnHeaderGroup/gchg_mouseDownDragUpHandler()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/spark/src/spark/components/GridColumnHeaderGroup.as:1112]
at
Function/<anonymous>()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/spark/src/spark/utils/MouseEventUtil.as:104]

View is null because columnIndex is -1.

Thanks for help.