Yep it means the addon is in Firefox

Could you reset firefox https://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-problems?utm_expid=65912487-41.djHNRQY0RhaLvvtvcd0BQA.2&utm_referrer=https%3A%2F%2Fwww.google.co.uk%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3D%26esrc%3Ds%26source%3Dweb%26cd%3D1%26ved%3D0CCIQFjAA%26url%3Dhttps%253A%252F%252Fsupport.mozilla.org%252Fen-US%252Fkb%252Freset-firefox-easily-fix-most-problems%26ei%3D8FPBU7WFD4WVO8X5gfgH%26usg%3DAFQjCNFtaKEVZ_YyFC_12I9TEu28byOooQ%26bvm%3Dbv.70810081%2Cd.ZWU
You will have to re-install your addons that you use though