[FIX] Increasing unread counter twice for new threads in DMs or with mentions

[KevLehman]

Proposed changes (including videos or screenshots)

• Unread messages count won't be incremented when the message sent is on a thread (thread count is treated different)

Issue(s)

• No open issue.
• Issue description: when a user answers a direct message by answering in a thread, the unread counter next to user's name will mark 2 instead of 1.

Steps to test or reproduce

• Start a direct conversation with another person
• After the first message from the other one, instead of answering to the main conversation, write your reply in a thread\
• The other person will see a badge of 2 unread messages instead of 1 (since we sent just one message)

Further comments

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