mod_invites_register: Fix missing 'from' attribute (thanks Martin) This should probably cause a noisier error in Prosody, than the current > No hosts[from_host] (please report): <stanza> A stack trace would have been useful, for example.

This module blocks configured queries that change server state.

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

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