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/utilsgtk.cpp

@@ -119,7 +119,7 @@ void wxDisplaySizeMM( int *width, int *height )
 
 void wxGetMousePosition( int* x, int* y )
 {
-    gdk_window_get_pointer( (GdkWindow*) NULL, x, y, (GdkModifierType*) NULL );
+    gdk_window_get_pointer( NULL, x, y, NULL );
 }
 
 bool wxColourDisplay()