Seems it's not a bug in thunderbird, but a bug in enigmail package (and possibly all extensions packages that uses thunderbird directory instead of thunderbird-addons) - it has '/usr/lib/thunderbird/extensions' directory, but should have '/usr/lib/thunderbird-addons/extensions'. So, when installation of new version of enigmail happens earlier than installation of thunderbird itself - this bug appears.
Looking wide I have to say that /usr/lib/thunderbird-addons directory becomes meaningless now, when we have one /usr/lib/thunderbird directory (without version suffix). May be it's time to make it just a symlink to /usr/lib/thunderbird (for compatibility reasons)?
Seems it's not a bug in thunderbird, but a bug in enigmail package (and possibly all extensions packages that uses thunderbird directory instead of thunderbird-addons) - it has '/usr/lib/ thunderbird/ extensions' directory, but should have '/usr/lib/ thunderbird- addons/ extensions' . So, when installation of new version of enigmail happens earlier than installation of thunderbird itself - this bug appears.
Looking wide I have to say that /usr/lib/ thunderbird- addons directory becomes meaningless now, when we have one /usr/lib/ thunderbird directory (without version suffix). May be it's time to make it just a symlink to /usr/lib/ thunderbird (for compatibility reasons)?