Not working in Waterfox. Fix proposed.

[andreacc]

File classes.js have following lines:
browser.browserAction.setBadgeBackgroundColor({color: null});
browser.browserAction.setBadgeText({text: null});

But Waterfox, as well as Firefox versions below 59 don't accept null value for such functions. Is it possible to change to something like 'white' and 'on' so the addon works on Waterfox? Thanks.