The chat-history-fill-in code had logic to avoid appending two
messages when a message appeared in both the log and the pending
messages. But it wasn't working because of an incorrect object field
name.
Additionally, the code was previously keeping the copy of the message
from the log, and suppressing the copy from pending. But that meant
that once the previous bug was fixed, it would think it had only shown
old messages, and so it would create a source but not notify it. So
fix it to suppress the log message and show the pending message.
https://bugzilla.gnome.org/show_bug.cgi?id=645612
d2de0865bf