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 attempts to sanitize XHTML-IM messages.
It does **not** attempt to sanitize any CSS embedded in `style`
attributes, these are instead stripped by default.
Configuration
=============
Option Type Default
------------------------ --------- ---------
`strip_xhtml_style` boolean `true`
`bounce_invalid_xhtml` boolean `false`