mod_muc_badge: If room has no title use localpart of room's jid (fixes #1767) Without this patch Prosody shows an HTTP 500 error (Lua 5.1) or a "nil" label in the SVG badge (Lua 5.2) if room has no title set.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```