partial fix for bugscape bug 4458, presence stopped working. notify clear addresses is being defined in msgHdrViewAddresses. r=suresh@netscape.com, sr=mscott@netscape.com

mailnews/base/resources/content/msgHdrViewOverlay.js

@@ -223,7 +223,7 @@ var messageHeaderSink = {
       // WARNING: This is the ONLY routine inside of the message Header Sink that should 
       // trigger a reflow!
       
-      if (this.NotifyClearAddresses != undefined)
+      if (NotifyClearAddresses != undefined)
         NotifyClearAddresses();
 
       ClearHeaderView(gCollapsedHeaderView);