Use empty() to check for emptiness.

Qt/Components/pqSettingsDialog.cxx

@@ -37,6 +37,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "pqProxyWidget.h"
 #include "pqSearchBox.h"
 #include "pqServer.h"
+#include "pqServerManagerModel.h"
 #include "pqSettings.h"
 #include "pqUndoStack.h"
 #include "vtkNew.h"
@@ -52,6 +53,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <QKeyEvent>
 #include <QMap>
+#include <QPointer>
 #include <QPushButton>
 #include <QScrollArea>
 #include <QSpacerItem>
@@ -65,6 +67,8 @@ class pqSettingsDialog::pqInternals
   // Map from tab indices to stack widget indices. This is needed because there
   // are more widgets in the stacked widgets than just what we add.
   QMap<int, int> TabToStackedWidgets;
+
+  QPointer<pqServer> Server;
 };
 
 bool pqSettingsDialog::ShowRestartRequired = false;
@@ -87,6 +91,8 @@ pqSettingsDialog::pqSettingsDialog(QWidget* parentObject, Qt::WindowFlags f)
   QList<vtkSMProxy*> proxies_to_show;
 
   pqServer* server = pqActiveObjects::instance().activeServer();
+  this->Internals->Server = server;
+
   vtkNew<vtkSMProxyIterator> iter;
   iter->SetSession(server->session());
   iter->SetModeToOneGroup();
@@ -167,6 +173,9 @@ pqSettingsDialog::pqSettingsDialog(QWidget* parentObject, Qt::WindowFlags f)
   this->onTabIndexChanged(0);
 
   this->filterPanelWidgets();
+
+  pqServerManagerModel* smmodel = pqApplicationCore::instance()->getServerManagerModel();
+  this->connect(smmodel, SIGNAL(serverRemoved(pqServer*)), SLOT(serverRemoved(pqServer*)));
 }
 
 //-----------------------------------------------------------------------------
@@ -176,6 +185,16 @@ pqSettingsDialog::~pqSettingsDialog()
   this->Internals = NULL;
 }
 
+//-----------------------------------------------------------------------------
+void pqSettingsDialog::serverRemoved(pqServer* server)
+{
+  // BUG #14957: Close this dialog if the server session closes.
+  if (this->Internals->Server == server)
+    {
+    this->close();
+    }
+}
+
 //-----------------------------------------------------------------------------
 void pqSettingsDialog::clicked(QAbstractButton *button)
 {

Qt/Components/pqSettingsDialog.h

@@ -35,6 +35,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <QDialog>
 #include "pqComponentsModule.h"
 
+class pqServer;
 class QAbstractButton;
 class vtkSMProperty;
 
@@ -62,6 +63,10 @@ private slots:
 
   void filterPanelWidgets();
 
+  /// Callback for when pqServerManagerModel notifies the application that the
+  /// server is being removed. We close the dialog.
+  void serverRemoved(pqServer*);
+
 signals:
   void filterWidgets(bool showAdvanced, const QString& text);