rem: if (aDragSession) { 
add:   if (aDragSession && aDragSession.sourceNode) { 
context:   canDrop: function (aEvent, aDragSession)  {    var target = aEvent.target;    if (aDragSession) { // this function gets its API abused by onDragStart      var orientation = BookmarksMenu.getBTOrientation(aEvent, target);      if (target == aDragSession.sourceNode ||          (target == aDragSession.sourceNode.previousSibling &&           orientation == BookmarksUtils.DROP_AFTER) ||          (target == aDragSession.sourceNode.nextSibling &&           orientation == BookmarksUtils.DROP_BEFORE))        return false;    }    return BookmarksMenu.isBTBookmark(target.id)       &&            target.id != "NC:SystemBookmarksStaticRoot" &&           target.id.substring(0,5) != "find:"         ||           target.id == "BookmarksMenu"                ||           target.id == "bookmarks-button"             ||           target.id == "bookmarks-chevron"            ||           target.id == "bookmarks-ptf";  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/fa56940e966c543cd35c0b4c1df0ce55e3396ca9/bookmarksMenu.js/clean/xpfe/components/bookmarks/resources/bookmarksMenu.js