don't use annoying and unneeded in C++ casts of NULL to "T *" in all other files neither

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/docmdi.h

@@ -84,7 +84,7 @@ public:
     inline wxView *GetView(void) const { return m_childView; }
     inline void SetDocument(wxDocument *doc) { m_childDocument = doc; }
     inline void SetView(wxView *view) { m_childView = view; }
-    bool Destroy() { m_childView = (wxView *)NULL; return wxMDIChildFrame::Destroy(); }
+    bool Destroy() { m_childView = NULL; return wxMDIChildFrame::Destroy(); }
 
 protected:
     void Init();