Reassigning attendees in breakout room removes everyone from the room

[Antreesy]

To reproduce:

• Alice is in call in room 1
• Moderator reassign participants, keeping Alice in room 1
• Alice gets page-not-found

When checking system messages, everyone got removed from BR, then only selected participants are added back.

Looks like $removals on API side are not filled correctly.

spreed/lib/Service/BreakoutRoomService.php

Lines 224 to 241 in e0f1906

	foreach ($breakoutRooms as $breakoutRoom) {
	$breakoutRoomParticipants = $this->participantService->getParticipantsForRoom($breakoutRoom);
	foreach ($breakoutRoomParticipants as $participant) {
	$attendee = $participant->getAttendee();
	if ($attendee->getActorType() === Attendee::ACTOR_USERS && in_array($attendee->getActorId(), $userIds, true)) {
	if ($participant->hasModeratorPermissions()) {
	// Can not remove moderators with this method
	throw new InvalidArgumentException('moderator');
	}
	$removals[] = [
	'room' => $breakoutRoom,
	'participant' => $participant,
	];
	}
	}
	}

Originally posted by @Antreesy in #11649 (comment)