Last part from weak ref patch for event sink disconnection

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51111 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/tracker.h

@@ -73,7 +73,7 @@ struct wxTrackableBase {
     wxTrackerNode* GetFirst( ){ return m_first; }
 
     // If trying to copy this object, then do not copy its ref list.
-    wxTrackableBase& operator = (const wxTrackableBase& other) { return *this; }
+    wxTrackableBase& operator = (const wxTrackableBase& WXUNUSED(other)) { return *this; }
     
 protected:    
     wxTrackerNode *m_first;