JavaScript error on add/edit form for users without administer polls permission

The form for adding/editing a poll triggers a JavaScript error for users that do not have the administer polls permission. This causes the Poll Settings block to be collapsed without means to open it.
I have traced it to advpoll-form.js, line 56:

if ($("input.settings-writeins").attr("checked")) {

Apparently, when the user does not have the administer polls permission, settings-writeins is not there, $("input.settings-writeins") returns an empty list and the $("input.settings-writeins").attr() fails.
A possible fix is to change the line to this:

if ($("input.settings-writeins").length && $("input.settings-writeins").attr("checked")) {