Dialog refuses to open: Need input table spec to configure dialog

Hello,

I have a problem with DialogComponentColumnNameSelection in the node dialog.  I have an optional port, and when the input port is not connected, the dialog won't start with an error message: "need input table spec to configure dialog".

I already tried to check, whether the port is connected or not, see the following code snippet:

public class SeesarViewerNodeDialog extends DefaultNodeSettingsPane {

    private final SettingsModelString m_moleculeColumnName;
    private final SettingsModelString m_proteinColumnName;

    protected SeesarViewerNodeDialog() {
        super();

        m_moleculeColumnName = SeesarViewerNodeModel.createSettingsMoleculeColumnName();
        addDialogComponent(new DialogComponentColumnNameSelection(
                m_moleculeColumnName,
                "Molecule column", 0,
                SeesarViewerNodeModel.ACCEPTED_MOLECULE_COLUMN_CLASSES) {

                    @Override
                    protected void checkConfigurabilityBeforeLoad(
                            PortObjectSpec[] specs)
                            throws NotConfigurableException {
                        super.checkConfigurabilityBeforeLoad(specs);
                        m_moleculeColumnName.setEnabled(specs[0] != null);
                    }
                });
        :

But the error message remains when trying to open the dialog.  Can anyone help here?

Best regards, Frank