Upgrade to ejabberd 18.06
Ejabberd upgrade process
There are few option changes in this version. Please check the blogpost: https://www.process-one.net/blog/ejabberd-18-06/
Note: Starting with ejabberd 18.06, ejabberd will not ignore unknown options and doesn't allow to have options with malformed values. The rationale for this is to avoid unexpected behaviour during runtime, i.e. to conform to “fail early” approach. FOR PACKAGE BUILDERS: You must ensure your configuration is valid.
You may cleanup SQL database if you are upgrading from ejabberd 18.04 or older, and running an SQL backend for mod_irc.
mod_irc had been obsoleted, the module is still available in ejabberd-contrib and can be installed as external module anyway. If you're not using that module or stop using it, you can safely remove the irc_custom SQL table.