Set wxPendingEvents to NULL after deletion

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@20206 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/mac/app.cpp

@@ -678,6 +678,7 @@ void wxApp::CleanUp()
         delete wxWinMacControlList ;
     }
     delete wxPendingEvents;
+    wxPendingEvents = NULL;
 
 #if wxUSE_THREADS
     delete wxPendingEventsLocker;

src/mac/carbon/app.cpp

@@ -678,6 +678,7 @@ void wxApp::CleanUp()
         delete wxWinMacControlList ;
     }
     delete wxPendingEvents;
+    wxPendingEvents = NULL;
 
 #if wxUSE_THREADS
     delete wxPendingEventsLocker;