If an Error is thrown in the append method of a widget, the panelDiv should be removed

[shakty]

Or not appended at all before. However, some widgets might want to know the exact location of the appended widget on the page, so this is not a good solution.

Probably, the best is a try-catch here:

w.bodyDiv = W.append('div', w.panelDiv, { className: tmp });

Or enabling a return error code.