[FIX] mail: unread counter on new message in non pinned DM

When a new message arrived in a non pinned DM, the unread counter was
incremented twice ; once because the channel info (along with its unread
counter) was fetched from the server as the channel wasn't in the JS cache yet,
and once when adding the message in the JS.

With this rev., we only increment the unread counter when a new message arrives
if its channel is already in the JS cache.

0 files changed, 0 insertions, 0 deletions