I really don't see this as a lubuntu-artwork bug this is more with lxsession package wihch tracks bugs for default app-for lxsession. Also if you want a workaroudn for the time being click the more button and set nemo as the file manager that way.
** Project changed: lubuntu-artwork => lxsession (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1466288 Title: Cannot set 'nemo' as the defaut file manager To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lxsession/+bug/1466288/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs