[dovecot/core] 6699d5: auth: Fix auth_request_is_disabled_master_user

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 6699d5ab6a1e6366226fff755dc5f6e34ccee8b4
      https://github.com/dovecot/core/commit/6699d5ab6a1e6366226fff755dc5f6e34ccee8b4
  Author: Aki Tuomi <aki.tuomi at dovecot.fi>
  Date:   2017-12-05 (Tue, 05 Dec 2017)

  Changed paths:
    M src/auth/auth-request.c

  Log Message:
  -----------
  auth: Fix auth_request_is_disabled_master_user

I assumed that lack of passdb means master authentication,
but e.g. gssapi does not require a passdb. Instead, check
that if requested_login_uset is non-null then check passdb is
non-null too.

Fixes auth: Panic: file auth-request.c: line 716 (auth_request_is_disabled_master_user): assertion failed: (request->requested_login_user != NULL)