File 0001-Only-show-system-bus-tab-if-system-bus-is-present.patch of Package mingw64-libqt5-qttools

--- a/src/qdbus/qdbusviewer/mainwindow.cpp        2020-07-26 19:42:32.215475717 +0000
+++ b/src/qdbus/qdbusviewer/mainwindow.cpp        2020-07-26 19:42:47.471351997 +0000
@@ -41,7 +41,8 @@
 #include <QtCore/QSettings>
 
 MainWindow::MainWindow(QWidget *parent)
-    : QMainWindow(parent)
+    : QMainWindow(parent),
+      systemBusViewer(0)
 {
     QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
     QAction *quitAction = fileMenu->addAction(tr("&Quit"), this, &QWidget::close);
@@ -61,9 +62,12 @@
     setCentralWidget(tabWidget);
 
     sessionBusViewer = new QDBusViewer(QDBusConnection::sessionBus());
-    systemBusViewer = new QDBusViewer(QDBusConnection::systemBus());
     tabWidget->addTab(sessionBusViewer, tr("Session Bus"));
+    QDBusConnection systemBus = QDBusConnection::systemBus();
+    if (systemBus.isConnected()) {
+        systemBusViewer = new QDBusViewer(systemBus);
     tabWidget->addTab(systemBusViewer, tr("System Bus"));
+    }
 
     restoreSettings();
 }
@@ -109,9 +113,11 @@
     sessionBusViewer->saveState(&settings);
     settings.endGroup();
 
+    if (systemBusViewer) {
     settings.beginGroup(systemTabGroup());
     systemBusViewer->saveState(&settings);
     settings.endGroup();
+    }
 }
 
 void MainWindow::restoreSettings()
@@ -124,7 +130,9 @@
     sessionBusViewer->restoreState(&settings);
     settings.endGroup();
 
+    if (systemBusViewer) {
     settings.beginGroup(systemTabGroup());
     systemBusViewer->restoreState(&settings);
     settings.endGroup();
+    }
 }