CSSTUDIO-3017 Only display the configuration window when a leaf representing a PV was clicked on.

Author: abrahamwolk

app/alarm/ui/src/main/java/org/phoebus/applications/alarm/ui/tree/AlarmTreeView.java

@@ -649,10 +649,12 @@ private void addClickSupport()
                 return;
 
             final AlarmTreeItem<?> item = tree_view.getSelectionModel().getSelectedItems().get(0).getValue();
-            final ItemConfigDialog dialog = new ItemConfigDialog(model, item);
-            DialogHelper.positionDialog(dialog, tree_view, -150, -300);
-            // Show dialog, not waiting for it to close with OK or Cancel
-            dialog.show();
+            if (item instanceof AlarmClientLeaf alarmClientLeaf) {
+                final ItemConfigDialog dialog = new ItemConfigDialog(model, alarmClientLeaf);
+                DialogHelper.positionDialog(dialog, tree_view, -150, -300);
+                // Show dialog, not waiting for it to close with OK or Cancel
+                dialog.show();
+            }
         });
     }