Regression: Exception on notification when addinf someone in room via…

… mention (#14251)

app/lib/server/lib/sendNotificationsOnMessage.js

@@ -3,7 +3,7 @@ import moment from 'moment';
 import { hasPermission } from '../../../authorization';
 import { settings } from '../../../settings';
 import { callbacks } from '../../../callbacks';
-import { Subscriptions } from '../../../models';
+import { Subscriptions, Users } from '../../../models/server';
 import { roomTypes } from '../../../utils';
 import { callJoinRoom, messageContainsHighlight, parseMessageTextPerUser, replaceMentionedUsernamesWithFullNames } from '../functions/notifications';
 import { sendEmail, shouldNotifyEmail } from '../functions/notifications/email';
@@ -36,6 +36,21 @@ export const sendNotification = async ({
 		return;
 	}
 
+	if (!subscription.receiver) {
+		subscription.receiver = [
+			Users.findOneById(subscription.u._id, {
+				fields: {
+					active: 1,
+					emails: 1,
+					language: 1,
+					status: 1,
+					statusConnection: 1,
+					username: 1,
+				},
+			}),
+		];
+	}
+
 	const [receiver] = subscription.receiver;
 
 	const roomType = room.t;