ux: bug fix: Do not show placeholder on unrelated threads
Fixes #1793 (closed)
When opening a subthread we, actually, have 2 threads screen live at the same time:
- the one for the root thread
- the one for the subthread
When publishing a message from the subthread, both thread instances will receive a willPublish$
value and will show the placeholder on both thread.
The condition to remove the placeholder is that the number of messages in the thread have changed. This is never true for the root thread (thus the placeholder never disappearing).
This PR fixes the problem by filtering publish events that are not directly related to the thread being displayed