fix: #8293, don't show error if there are no self messages

public/src/client/chats.js

@@ -194,6 +194,9 @@ define('forum/chats', [
 			if (e.target === components.get('chat/input').get(0)) {
 				// Retrieve message id from messages list
 				var message = components.get('chat/messages').find('.chat-message[data-self="1"]').last();
+				if (!message.length) {
+					return;
+				}
 				var lastMid = message.attr('data-mid');
 				var inputEl = components.get('chat/input');