I have it too in 65.0.1 (64-bit). With the latest update, the Web Developer
Tools > Console is empty too (no output log, no input possibility, just blank
white space).
I guess it only works because the built-in Icecat package is 8 major versions
behind the latest stable (52.3.0 instead of 60.3.0), which doesn't seem to be
a good long-term solution :/
I wonder if there's a reason for Abrowser to exist. I don't see any security
or other advantages in Abrows
I have similar faulty icons with some GNOME applications, but not with
Abrowser. I think it's usually related to the default custom theme coming
with Trisquel MATE desktop installation. You may try another theme in System
> Preferences > Look and Feel > Appearance > "Theme" tab.