Fix a threading issue in AppLogController

Fixes #392

nymea-app/applogcontroller.cpp

@@ -36,6 +36,7 @@
 #include <QClipboard>
 #include <QGuiApplication>
 #include <QDir>
+#include <QMutexLocker>
 
 QtMessageHandler AppLogController::s_oldLogMessageHandler = nullptr;
 
@@ -161,6 +162,7 @@ void AppLogController::logMessageHandler(QtMsgType type, const QMessageLogContex
 
 void AppLogController::append(const QString &message, AppLogController::Type type)
 {
+    QMutexLocker locker(&m_mutex);
     QString finalMessage = message + "\n";
     m_logFile.write(finalMessage.toUtf8());
     m_logFile.flush();

nymea-app/applogcontroller.h

@@ -35,6 +35,7 @@
 #include <QFile>
 #include <QQmlEngine>
 #include <QAbstractListModel>
+#include <QMutex>
 
 class AppLogController : public QAbstractListModel
 {
@@ -86,6 +87,7 @@ private:
     QFile m_logFile;
     QStringList m_buffer;
     QList<Type> m_types;
+    QMutex m_mutex;
 };
 
 #endif // APPLOGCONTROLLER_H