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/common/dpycmn.cpp

@@ -98,11 +98,7 @@ public:
     virtual bool OnInit() { return true; }
     virtual void OnExit()
     {
-        if ( gs_factory )
-        {
-            delete gs_factory;
-            gs_factory = NULL;
-        }
+        wxDELETE(gs_factory);
     }
 
     DECLARE_DYNAMIC_CLASS(wxDisplayModule)