Avoid resetting global cursor if no global cursor is set

see #17503

(cherry picked from commit 5819b9cbc5)

src/gtk/cursor.cpp

@@ -384,7 +384,10 @@ bool wxIsBusy()
 }
 
 void wxSetCursor( const wxCursor& cursor )
+{
+    //if (cursor.IsOk() || g_globalCursor.IsOk())
     {
         g_globalCursor = cursor;
         SetGlobalCursor(cursor);
     }
+}