Qt: fixed result of TQtWidgetSet.SetFocus(), in case when handle param is invalid.

git-svn-id: trunk@27379 -

lcl/interfaces/qt/qtwinapi.inc

@@ -4818,6 +4818,7 @@ end;
  ------------------------------------------------------------------------------}
 function TQtWidgetSet.SetFocus(hWnd: HWND): HWND;
 begin
+  Result := 0;
   if hwnd<>0 then
   begin
     {$ifdef VerboseFocus}