_thingConversations hangs if a comment thread is completely deleted

(Bug, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y284oe not found, )

Conversations

Summary: Nothing displays -- it appears to be a complete hang.

What's actually going on is that the client is crashing, because it's trying to take the "head" comment and there isn't one.

Fortunately, this appears to be pretty easy to fix, by making the ConvNode in ConversationGadget Option[ConvNode] instead, and adjusting all the rendering accordingly.