Invisible icon on menu bar depending of Mac OS

[HQuatre]

First, many many thank for your add-on ! My monthly datas limit is... 3Go

Something strange appears depending of the Mac OS and FireFox with black theme named "Modern Dark" :

• with OS 10.13.6, the icon is correctly in video inverse on the menu bar, that is white on black background : visible
• with OS 14.8.1, the icon is black on black background : invisible but the info-bubble is OK.

Obviously, the Firefox have note the same version on the both Mac OS (and the both Mac machines).

Every OS and App are uptodate as much as possible.

Thanks in advance and sorry for my huggly english.

Sergio