Ignore events from sources whose state set is empty
Ignore events from sources whose state set is empty

When we go to process any event, we always look for relevant states and
stop processing the event should the relevant states be missing. If the
event comes from a source with an empty state set, there's no point in
queueing it up for processing.

GNOME/orca,GNOME/orca,GNOME/orca,GNOME/orca