Full editing replies (not first-post) removes thread from portal

[Sama34]

Describe the bug
The toggle of portal display shouldn't be done when editing replies (not first-post). This currently causes the thread from being removed from portal.

To Reproduce
Steps to reproduce the behavior:

1. Mark a thread to be displayed in portal.
2. Full edit any reply (not first-post)
3. Save such reply with or without changes
4. See error

Expected behavior
Edit of replies should not affect the display status of any thread.

Additional context
https://community.mybb.com/thread-152216-post-1369097.html#pid1369097

[Sama34]

Thanks @8guawong for this report.