The problem is that in _handle_groupchat() we look for
STANZA_NS_STABLE_ID which will result in origin-id or stanza-id.
It seems like prosody servers send origin-id first, so this worked in
all my tests. But actually we cannot be sure of the order.
So far we stopped after the first element was found.
I only found xmpp_stanza_get_child_by_ns() and
xmpp_stanza_get_child_by_name() in libstrophe. But we need a combination
of both.
So I created stanza_get_child_by_name_and_ns() for Profanity. I need to
remember to upstream this to libstrophe later (if they really don't have
such a function).
Fix https://github.com/profanity-im/profanity/issues/1223
68af0aad65