rem: if (target.className == undefined) return; while (target.className != "dialog" && target.className != "frame" && target.className != "mainMenu") target = target.parentNode; 
add: if (target == null || target.className == undefined) return; while (target != null && target.className != "dialog" && target.className != "frame" && target.className != "mainMenu") target = target.parentNode; 
context:     _mouseDownListener: function(event) {        var target = tw_getEventTarget(event);        if (target.className == undefined) return;        while (target.className != "dialog" && target.className != "frame" && target.className != "mainMenu") target = target.parentNode;                       if (target.className != "dialog" && target.parentNode.className != "dialog") {            if (tw_Dialog.active != null) tw_Dialog.active.setActive(false);            if (tw_Frame.active.getMenu() != null && target.className != "mainMenu") tw_Frame.active.getMenu().close();        }    },
meta: 5515	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5515/f1782c774313ba79c127ba5da30580c5ce1f4c32/Frame.js/clean/src/thinwire/render/web/resources/Frame.js