wxGridCellAttr was using literal -1 to indicate "no alignment" which wasn't immediately obvious, use a new wxALIGN_INVALID (which has the same value) instead. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62727 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775