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

src/osx/window_osx.cpp

@@ -153,7 +153,7 @@ wxWindowMac::~wxWindowMac()
         if ( frame )
         {
             if ( frame->GetLastFocus() == this )
-                frame->SetLastFocus((wxWindow*)NULL);
+                frame->SetLastFocus(NULL);
             break;
         }
     }