Since the last Firefox update (58), when right clicking and going to sub-menu, the icons are no longer displayed. Even those whose I put an address in the configuration panel.

EDIT: sometimes it's working but sometimes not. I need to restart Firefox to correct the problem. Not very embarrassing but I have to say it.Maybe there is a latency to load the icons but I wait long time and nothing. And I use the classic version of Firefox 64bits.