Fix crash on opening torrent/magnet (uninitialized pointer). Closes #7739 #7723.

src/app/application.cpp

@@ -105,6 +105,7 @@ Application::Application(const QString &id, int &argc, char **argv)
     , m_running(false)
     , m_shutdownAct(ShutdownDialogAction::Exit)
     , m_commandLineArgs(parseCommandLine(this->arguments()))
+    , m_webui(nullptr)
 {
     qRegisterMetaType<Log::Msg>("Log::Msg");