SceneComposer: can't add Control to Linked Model

I’ve got a NPE when I tried to add Control to a JmeAssetLinkNode. Because AssetLinkChildren.getDataObject is null

Node Class : class com.jme3.gde.core.sceneexplorer.nodes.JmeAssetLinkNode
SEVERE [com.jme3.gde.core.scene.SceneApplication]: Uncaught exception thrown in Thread[AWT-EventQueue-0,6,main]
java.lang.NullPointerException
	at com.jme3.gde.core.sceneexplorer.nodes.actions.impl.NewCustomControlWizardAction.showWizard(NewCustomControlWizardAction.java:72)
	at com.jme3.gde.core.sceneexplorer.nodes.actions.AbstractNewControlWizardAction$1.actionPerformed(AbstractNewControlWizardAction.java:69)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
  ...

[java]

protected Object showWizard(Node node) {
    System.out.println("Node Class : " + node.getClass());
    WizardDescriptor wizardDescriptor = new WizardDescriptor(getPanels());
    // {0} will be replaced by WizardDesriptor.Panel.getComponent().getName()
    wizardDescriptor.setTitleFormat(new MessageFormat("{0}"));
    wizardDescriptor.setTitle("Create Custom Control");
    wizardDescriptor.putProperty("asset_manager", node.getLookup().lookup(ProjectAssetManager.class));
    wizardDescriptor.putProperty("project", node.getLookup().lookup(ProjectAssetManager.class).getProject()); // <-- NPE

[/java]

Is it possible to add Control or Linked Model should be read-only ? (I ask to know how to fix)

Yeah, just wire up the DataObject for the AssetLinkNodes special children object.