How to get my form handler to work?

[Viktor Nagy]

I would like to create a greasemonkey script that add a new form to GitLab and runs a function defined in the script when the form is submitted.

I can create the form, but submitting it does not invoke my handler function. What should I do differently?

https://www.dropbox.com/s/alr11uyksmb0c45/GitLab%20filters.user.js?dl=0