Use wxDELETE() and wxDELETEA() when possible.

Use wxDELETE[A]() functions which automatically NULL out their arguments after
deleting them instead of doing it manually.

Closes #9685.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64656 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/x11/app.cpp

@@ -195,10 +195,8 @@ bool wxApp::Initialize(int& argC, wxChar **argV)
 
 void wxApp::CleanUp()
 {
-    delete wxWidgetHashTable;
-    wxWidgetHashTable = NULL;
-    delete wxClientWidgetHashTable;
-    wxClientWidgetHashTable = NULL;
+    wxDELETE(wxWidgetHashTable);
+    wxDELETE(wxClientWidgetHashTable);
 
     wxAppBase::CleanUp();
 }