Bugfix: Clicking an icon in menu-entries has no effect in Firefox

This can be observed in Firefox 61.0.1 (64-Bit), I did not experience the same problem in Chrome or InternetExplorer.

How to reproduce:
- Open an existing Feature or Requirement.
- Open the [...]-menu on the right-hand top Corner
- Click the small of a menu entry (e.g. "Use requirements estimates" or "Delete requirement")
- The menu closes or not (depending on the entry that was chosen) but no effect has taken place.

Note: Clicking the text of the menu works fine. It's the Icon (e.g. the 'tick box' or the 'small garbage can') that does not work.

It's very frustrating not to be able to use the menu as it was obviously intended to be used.