[2.3.9] Accessing breakout rooms isn't possible when users are allowed to choose the room

[antwertinger]

Describe the bug
Since version 2.3.9 users will only see a blue background when they choose a breakout room for joining.
The following javascript error occurs:
TypeError: can't access property "find", n.users is undefined

To Reproduce
Steps to reproduce the behavior:

1. Moderator create breakout rooms and check the checkbox "Allow users to choose a breakout room to join"
2. User choose a room for joining

Expected behavior
Joining the breakout room

Actual behavior
Joining is not possible, javascript error occurs.

Screenshots

BBB version:
BigBlueButton Server 2.3.9 (2421)

Additional context
The bug exists since version 2.3.9 and might be caused by this commit aa0ea21

[ffdixon]

Thanks for finding this issue -- confirmed it is in 2.3.9.

[danimo]

What was the last known version? 2.3.7 or 2.3.8?

[antobinary]

Before 2.3.9 we had 2.3.8 https://github.com/bigbluebutton/bigbluebutton/releases

[danimo]

Sorry, this meant to say "last known GOOD version"? (asking for a temp. rollback).

[antwertinger]

Last version without the problem was 2.3.8

[danimo]

We did some testing: I supect that aa0ea21 is bad. It introduces a filter by userId, which might not be available in the manual assign case. Note this is only a hypothesis, I have not yet tried to roll back the change.

[danimo]

Rolling back aa0ea21 indeed seems to help (with the obvious drawbacks of loosing the added protection).

[crosscodr]

The problem still exists in 2.3.10.
After choosing a breakout room from the drop-down-menu as normal user and press the button to join, the result is an empty blank page.
However, back in the main room, one can successfully join a breakout-room by going to Breakout-rooms in the left panel.

[antobinary]

Thanks @crosscodr !
@antonbsa was able to reproduce this variation here too and opened #12923 to track it.