fix "wrong type" error when using wxDataViewChoiceByIndexRenderer, closes #15955

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78168 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
fix assert in dataview sample, closes #16679

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78169 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775