do not overwrite ms_{hwnd,className} in wxTimerHiddenWindowModule::OnInit() in case they were already initialized

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_9_0_BRANCH@60669 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/timer.cpp

@@ -192,8 +192,10 @@ const wxChar *wxTimerHiddenWindowModule::ms_className = NULL;
 
 bool wxTimerHiddenWindowModule::OnInit()
 {
-    ms_hwnd = NULL;
-    ms_className = NULL;
+    // do not initialize ms_hwnd to ms_className to NULL here: it may happen
+    // that our GetHWND() is called before the modules are initialized if a
+    // timer is created from wxApp-derived class ctor and in this case we
+    // shouldn't overwrite it
 
     return true;
 }