Updates to keep OS/2 Frame apps from crashing on exit. Fixes WM_QUIT processing

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@8256 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/os2/frame.cpp

@@ -175,7 +175,7 @@ wxFrame::~wxFrame()
 
         if (wxTheApp->GetExitOnFrameDelete())
         {
-            ::WinPostMsg(GetHWND(), WM_QUIT, 0, 0);
+            ::WinPostMsg(NULL, WM_QUIT, 0, 0);
         }
     }
     wxModelessWindows.DeleteObject(this);