mod_rest: Fix nested message stanzas in XEP-0297 containers It's all a bit awkward because it doesn't normally use the whole schema directly, but rather checks which stanza type is used and picks out that property as a schema. Which also prevents references from working.

This module discards typing notifications sent to a bare host JID,
preventing error replies to be sent. These errors are harmless but can
be annoying sometimes if your client shows them prominently.