If there are no sessions, we don't need to run a query

[nickvergessen]

Should remove all those queries from our query log:

SELECT * FROM `oc_talk_guests` WHERE `session_hash` IN (NULL)

Called from

spreed/lib/Controller/RoomController.php

Lines 877 to 881 in 291e2c7

	$guestSessions = [];
	foreach ($participants['guests'] as $participant) {
	$guestSessions[] = sha1($participant['sessionId']);
	}
	$guestNames = $this->guestManager->getNamesBySessionHashes($guestSessions);

[rullzer]

Nice catch