Allow add PV item even if setpoint is not specified

Author: georgweiss

app/save-and-restore/app/src/main/java/org/phoebus/applications/saveandrestore/ui/configuration/ConfigurationController.java

@@ -380,7 +380,10 @@ public void commitEdit(Double value) {
                         userIdentity.isNull().get(),
                 dirty, configurationDescriptionProperty, configurationNameProperty, userIdentity));
 
-        addPvButton.disableProperty().bind(pvNameField.textProperty().isEmpty());
+        addPvButton.disableProperty().bind(Bindings.createBooleanBinding(() ->
+                pvNameField.textProperty().isEmpty().get() &&
+                        readbackPvNameField.textProperty().isEmpty().get(),
+                pvNameField.textProperty(), readbackPvNameField.textProperty()));
 
         readOnlyCheckBox.selectedProperty().bindBidirectional(readOnlyProperty);