schedule editor: cannot delete schedule item on firefox

[terceiro]

when I cilck the "x", the following exception happens.

TypeError: mouseEvent.path is undefinededit_schedule.js:114:27
    handleClickDelete http://dc19.localhost:8000/static/js/edit_schedule.js:114

from a quick google search it seems that mouseEvent.path is not available on firefox and some other browser that I don't recall.