[dovecot/core] aabc4a: auth: If passdbs are required, don't allow only ma...

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: aabc4ae9943c55fcb80963b3a3d3698d4488ba20
      https://github.com/dovecot/core/commit/aabc4ae9943c55fcb80963b3a3d3698d4488ba20
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2016-01-18 (Mon, 18 Jan 2016)

  Changed paths:
    M src/auth/auth.c

  Log Message:
  -----------
  auth: If passdbs are required, don't allow only master=yes passdbs.

This fixes a crash:

Panic: file auth-request.c: line 743 (auth_request_is_disabled_master_user):
assertion failed: (request->requested_login_user != NULL)

Which would happen because request->passdb=NULL because there are only
master passdbs. Even if only master passdb is actually needed, there should
still be a non-master passdb for non-master logins to specify what happens
to them.