Due to a trivial oversight the update_bacula_tables did not permit
upgrading from 7.4.x to 7.9.x. So I fixed the problem as well as a few
other things and have released a BETA 7.9.1 to bacula.org. Since this
is a beta release, I do not plan to release it to Source Forge.
Your help testing this will be much appreciated by other users, so I
encourage you to try it on different systems. I have thoroughly test it
on Ubuntu 16.04.