[FS9] Add missing null termination when serializing QStrings

The produced QByteArray was missing the null terminating character,
since QByteArray::append() only added up to and not including '\0'.
This was also the reason why sometimes planes did not change their
aircraft models properly.

src/plugins/simulator/fs9/fs9client.cpp

@@ -316,9 +316,6 @@ namespace BlackSimPlugin
             MultiPlayerPacketParser::writeSize(message, mpChangePlayerPlane.size());
             message = MultiPlayerPacketParser::writeMessage(message, mpChangePlayerPlane);
             CLogMessage(this).debug() << m_callsign << " connected to session.";
-            // Send it several times, since one got missed several times.
-            sendMessage(message);
-            sendMessage(message);
             sendMessage(message);
 
             m_timerId = startTimer(m_updateInterval.value(CTimeUnit::ms()));

src/plugins/simulator/fs9/multiplayerpacketparser.cpp

@@ -29,7 +29,7 @@ namespace BlackSimPlugin
 
             QByteArray writeValue(QByteArray data, const QString &value)
             {
-                data.append(qPrintable(value));
+                data.append(qPrintable(value), value.size() + 1);
                 return data;
             }