The result of calling NewControlId() must be assigned to wxWindowIDRef to be
accounted for correctly, otherwise the id was marked as free while a reference
to it still existed resulting in asserts in id management code when we
attempted to reuse it.
Closes#11604.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65059 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775