util.error: Fix error on conversion of invalid error stanza, fix #1805 Error stanzas should have an <error> element, but if you pass a stanza without one to util.error.from_stanza() it triggers an attempt to index a nil value, which this patch avoids. In the conditional, it should be safe to assume error_tag is non-nil since condition can't have those values then.

== 1.0 ==
- Roster providers
- Clustering
- World domination