Check welcome message length

To not try sending a null message to newly connected users if it's too
long. This is really unlikely to happen in practice, but better to do
so.

src/libserver/client.cpp

@@ -689,11 +689,16 @@ void Client::sendDirectMessages(const net::MessageList &msgs)
 	}
 }
 
-void Client::sendSystemChat(const QString &message, bool alert)
+bool Client::sendSystemChat(const QString &message, bool alert)
 {
-	d->msgqueue->send(
-		alert ? net::ServerReply::makeAlert(message)
-			  : net::ServerReply::makeMessage(message));
+	net::Message msg = alert ? net::ServerReply::makeAlert(message)
+							 : net::ServerReply::makeMessage(message);
+	if(msg.isNull()) {
+		return false;
+	} else {
+		d->msgqueue->send(msg);
+		return true;
+	}
 }
 
 void Client::receiveMessages()

src/libserver/client.h

@@ -221,7 +221,7 @@ class Client : public QObject {
 	 * @brief Send a message from the server directly to this user
 	 * @param message
 	 */
-	void sendSystemChat(const QString &message, bool alert = false);
+	bool sendSystemChat(const QString &message, bool alert = false);
 
 	bool isWebSocket() const;
 

src/libserver/session.cpp

@@ -364,8 +364,10 @@ void Session::joinUser(Client *user, bool host)
 
 	const QString welcomeMessage =
 		m_config->getConfigString(config::WelcomeMessage);
-	if(!welcomeMessage.isEmpty()) {
-		user->sendSystemChat(welcomeMessage);
+	if(!welcomeMessage.isEmpty() && !user->sendSystemChat(welcomeMessage)) {
+		user->log(Log()
+					  .about(Log::Level::Error, Log::Topic::Status)
+					  .message(QStringLiteral("Welcome message too long")));
 	}
 
 	// Make sure everyone is up to date