Raise version dialog if it already is open

Also register it as a window for the Window menu.

Task-number: QTCREATORBUG-14604
Change-Id: Ib52dcc193bf480ade14ca7c34b4dc10d6ec8fc4a
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/coreplugin/mainwindow.cpp

@@ -1098,8 +1098,11 @@ void MainWindow::aboutQtCreator()
         m_versionDialog = new VersionDialog(this);
         connect(m_versionDialog, &QDialog::finished,
                 this, &MainWindow::destroyVersionDialog);
-    }
+        ICore::registerWindow(m_versionDialog, Context("Core.VersionDialog"));
         m_versionDialog->show();
+    } else {
+        ICore::raiseWindow(m_versionDialog);
+    }
 }
 
 void MainWindow::destroyVersionDialog()