fix: #9503, dont error in markUnread if room doesnt exist

this prevents deleting the user if they are the only person in the chat room

src/messaging/unread.js

@@ -31,7 +31,7 @@ module.exports = function (Messaging) {
 	Messaging.markUnread = async (uids, roomId) => {
 		const exists = await Messaging.roomExists(roomId);
 		if (!exists) {
-			throw new Error('[[error:chat-room-does-not-exist]]');
+			return;
 		}
 		const keys = uids.map(uid => `uid:${uid}:chat:rooms:unread`);
 		return await db.sortedSetsAdd(keys, Date.now(), roomId);

test/user.js

@@ -541,6 +541,17 @@ describe('User', () => {
 			await Posts.upvote(result.postData.pid, 1);
 			assert(!await db.isSortedSetMember('users:reputation', uid));
 		});
+
+		it('should delete user even if they started a chat', async () => {
+			const socketModules = require('../src/socket.io/modules');
+			const uid1 = await User.create({ username: 'chatuserdelete1' });
+			const uid2 = await User.create({ username: 'chatuserdelete2' });
+			const roomId = await socketModules.chats.newRoom({ uid: uid1 }, { touid: uid2 });
+			await socketModules.chats.send({ uid: uid1 }, { roomId: roomId, message: 'hello' });
+			await socketModules.chats.leave({ uid: uid2 }, roomId);
+			await User.delete(1, uid1);
+			assert.strictEqual(await User.exists(uid1), false);
+		});
 	});
 
 	describe('passwordReset', () => {