Fix NULL window argument to wxEVT_KILL_FOCUS when creating a TLW.

Fix NULL window argument to wxEVT_KILL_FOCUS when creating a TLW.

wxTopLevelWindowMSW::CreateDialog first moved and resized the newly
created window and only then called SubclassWin(). Because native focus
change occurred when moving the window, HWND->wxWindow association
wasn't yet filled in and wxFindWinFromHandle() would return NULL.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69469 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775