Add global mute option

src/qt/qt_mainwindow.cpp

@@ -178,6 +178,7 @@ MainWindow::MainWindow(QWidget *parent)
     extern MainWindow *main_window;
     main_window = this;
     ui->setupUi(this);
+    status->setSoundGainAction(ui->actionSound_gain);
     ui->stackedWidget->setMouseTracking(true);
     statusBar()->setVisible(!hide_status_bar);
     statusBar()->setStyleSheet("QStatusBar::item {border: None; } QStatusBar QLabel { margin-right: 2px; margin-bottom: 1px; }");