var wrapFn = function (event) {
var eventNameSymbol = zoneSymbolEventNames[event.type];
if (!eventNameSymbol) {
eventNameSymbol = zoneSymbolEventNames[event.type] = zoneSymbol('ON_PROPERTY' + event.type);
}
If some calls function without parameter, if event is undefined zone crashes
In my case window.onbeforeunload is called from parent frame but zone wrapFn does not check for event parameter and trys to get it from map, and since event is undefined it crashes