Test ab-err-s0002-4

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result"/>
   <p:group>
      <p:group>
         <p:identity name="step">
            <p:with-input>
               <doc/>
            </p:with-input>
         </p:identity>
      </p:group>
      <p:identity name="step"/>
   </p:group>
</p:declare-step>