Jenkins.instance.getAllItems(AbstractProject).each { p ->
  def slaveLabel = new hudson.model.labels.LabelAtom("Slave");
  def node = p.getAssignedLabel().toString();
  if (node != null) {
    if ("null".equals(node)) {
        println "Setting new node for: " +  p.fullDisplayName + "(" + node + ")";
      	p.setAssignedLabel(slaveLabel);
      	p.save();
    }
  }
}