Fix Add-ons not working in Firefox 35

Firefox 35 has been pushed to the Stable channel recently by Mozilla and while the majority of users did not notice any incompatibilities or issues, some users noticed that one or multiple of installed browser add-ons stopped working suddenly.

This includes popular add-ons such as Ghostery or Adblock Plus among others. While the add-ons are still showing up as installed in Firefox, their functionality appears broken in Firefox 35.