mod_admin_blocklist: Fix traceback due to misplaced parenthesis
get_jids_with_role() throws an exception when 'host' is nil since
Prosody trunk rev 7ca5645f46cd
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summary: 'Anonymous unique occupant identifiers for MUCs'
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Introduction
============
This module implements [XEP-0421: Anonymous unique occupant identifiers for
MUCs](https://xmpp.org/extensions/xep-0421.html).
TODO
====
- Subject messages
Compatibility
=============
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0.12 Built-in, not needed
0.11 Works; except in MUC-PMs
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