mod_sasl2_fast: Improve handling when SASL profile unexpectedly lacks CB
This fixes a traceback reported by riau, but likely does not solve the
underlying cause, whatever that is.
# Introduction
This module exposes users [microblogging][xep277] on Prosodys built-in HTTP server.
# Usage
With default HTTP settings, the microblog of `user@example.com` would be
seen at `https://example.com:5281/atom/user`.
# Configuration
The module itself has no options. However it uses the access control
mechanisms in PubSub, so users must reconfigure their microblogging node
to allow access, by setting `access_model` to `open`.
E.g. Gajim has UI for this, look for "Personal Events" → "Configure
services".