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/gtk/dataview.cpp

@@ -2621,7 +2621,7 @@ void wxDataViewColumn::SetBitmap( const wxBitmap &bitmap )
     {
         GtkImage *gtk_image = GTK_IMAGE(m_image);
 
-        GdkBitmap *mask = (GdkBitmap *) NULL;
+        GdkBitmap *mask = NULL;
         if (bitmap.GetMask())
             mask = bitmap.GetMask()->GetBitmap();