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/motif/bmpmotif.h

@@ -24,7 +24,7 @@ public:
         m_armPixmap = (WXPixmap)NULL;
         m_insensPixmap = (WXPixmap)NULL;
         m_image = (WXImage)NULL;
-        m_display = (WXDisplay*)NULL;
+        m_display = NULL;
         SetColoursChanged();
     }