master: service(imap): child xxxx killed with signal 11

Dear Maintainer,

I have several dovecot installations, all of them stopped working with the upgrade from .16 to .17. Maybe I am missing something, or it's a bug. All I can see is a signal 11 after each login attempt.

Attached you can find a sysreport plus a core dump, both from different states of configuration (I reverted the core-dump settings later on) of the same server, but the effect has been the same ever since upgrading. I have other servers that use pam (not mariadb) and local maildirs that show the same behavior.

For now, I have downgraded all servers, if needed I could run some more tests.

Thank you for checking & cheers, Lukas