Lyubo Marinov
8cfc83f18c
Protect against late PARTICIPANT_JOINED
Like the preceding commit "ref(base/conference): clear the 'conference'
field on WILL_LEAVE", this commit is part of the story how we are to
deal with conferences which take noticeable time to leave.
If a leave is delayed and the leaving JitsiConference manages to sneak a
PARTICIPANT_JOINED in, it may create a remote participant who even
collides with the local participant.