Remove the item before notifying about it in wxDataViewIndexListModel.

Remove the item before notifying about it in wxDataViewIndexListModel.

Remove the item from the internal representation of the model before calling
ItemDeleted() callback so that the callback sees the model in a consistent
state.

This is more consistent with the other callbacks (e.g. ItemAdded()) and other
models (e.g. wxDataViewVirtualListModel) and should fix crashes in wxOSX
version of the control.

Closes #13753.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69990 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775