Prevent type error from loading non element

[timja]

I haven't managed to track down why this happens but I get a type error when loading configure job screens (at least freestyle).

The changed function gets called 3 times for me and the third one is not a dom element, it's an array containing two functions.

this is a work around but shouldn't cause any harm

(this isn't the error from https://github.com/jenkinsci/bom/pull/1133 but it's the first error I saw loading the page)