fix(AppManager): Don't create temporary copy of argc

QApplication takes argc by reference, so copying it in to AppManager's
constructor causes QApplication's to have an invalid reference once AppManager's
constructor returns.

Instead just reference main's argc.

Fix qTox#6641

src/appmanager.cpp

@@ -162,7 +162,7 @@ bool toxURIEventHandler(const QByteArray& eventData, void* userData)
 }
 } // namespace
 
-AppManager::AppManager(int argc, char** argv)
+AppManager::AppManager(int& argc, char** argv)
     : qapp((preConstructionInitialization(), new QApplication(argc, argv)))
     , messageBoxManager(new MessageBoxManager(nullptr))
     , settings(new Settings(*messageBoxManager))

src/appmanager.h

@@ -36,7 +36,7 @@ class AppManager : public QObject
     Q_OBJECT
 
 public:
-    AppManager(int argc, char** argv);
+    AppManager(int& argc, char** argv);
     ~AppManager();
     int run();