Enable/Disable "detach-view" correctly after DnD

Enables detach-view in the target window if dropping creates the first split.

Disables in the original window if one view is left after DnD.

src/ViewManager.cpp

@@ -642,6 +642,11 @@ SessionController *ViewManager::createController(Session *session, TerminalDispl
     connect(session, &Konsole::Session::selectionChanged, controller, &Konsole::SessionController::selectionChanged);
     connect(view, &Konsole::TerminalDisplay::destroyed, controller, &Konsole::SessionController::deleteLater);
 
+    // The controller is destroyed when the (split) view is drag-dropped to a different window
+    connect(controller, &QObject::destroyed, this, [this] {
+        toggleActionsBasedOnState();
+    });
+
     // if this is the first controller created then set it as the active controller
     if (_pluggedController.isNull()) {
         controllerChanged(controller);

src/widgets/ViewSplitter.cpp

@@ -378,10 +378,12 @@ void Konsole::ViewSplitter::dropEvent(QDropEvent *ev)
 
             Qt::Orientation orientation = droppedEdge == Qt::LeftEdge || droppedEdge == Qt::RightEdge ? Qt::Horizontal : Qt::Vertical;
 
+            // Add the display so it can be counted correctly by ViewManager
+            addTerminalDisplay(source, orientation, behavior);
+
             // topLevel is the splitter that's connected with the ViewManager
             // that in turn can call the SessionController.
             Q_EMIT getToplevelSplitter()->terminalDisplayDropped(source);
-            addTerminalDisplay(source, orientation, behavior);
             source->setVisible(true);
             currentDragTarget = nullptr;
         }