Uncaught ReferenceError: node is not defined when using horizontal=True

[leibowitz]

Checklist

• [x] This issue is not about installing previous versions of django-smart-selects older than 1.2.8. I understand that previous versions are insecure and will not receive any support whatsoever.
• [x] I have verified that that issue exists against the master branch of django-smart-selects.
• [x] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• [x] I have debugged the issue to the smart_selects app.
• [x] I have reduced the issue to the simplest possible case.
• [x] I have included all relevant sections of models.py, forms.py, and views.py with problems.
• [x] I have used GitHub Flavored Markdown to style all of my posted code.

Steps to reproduce

1. Use ManyToMany field with horizontal=True and add model to admin
2. Revert https://github.com/jazzband/django-smart-selects/commit/00b533c9aa057ee008c363cea3c75633e169b4b3 or use the changes in https://github.com/jazzband/django-smart-selects/pull/298
3. See an error in the console when accessing admin page with the field

Actual behavior

Error:

chainedm2m.js:123 Uncaught ReferenceError: node is not defined
    at Object.success (chainedm2m.js:123)
    at fire (jquery.js:3291)
    at Object.fireWith [as resolveWith] (jquery.js:3421)
    at done (jquery.js:9533)
    at XMLHttpRequest.<anonymous> (jquery.js:9785)

https://github.com/jazzband/django-smart-selects/blob/656e48579c7c37970bbd54ed7205aa029e6fd73a/smart_selects/static/smart-selects/admin/js/chainedm2m.js#L122-L123

Expected behavior

No errors

[leibowitz]

It seems to be because it's using strict mode and the variable node has not been defined