SOAPUtils's transformToStringArray() always returns an empty String array

<member>
  <name>customFieldValues</name>
 
  ...
    <value>
      <struct>
        <member>
          <name>customfieldId</name>
          <value>customfield_10100</value>
        </member>
      </struct>
    </value>

    <value>
      <struct>
        <member>
          <name>customfieldId</name>
          <value>customfield_10100</value>
        </member>

        <member>
          <name>key</name>
          <value>1</value>
        </member>
      </struct>
    </value>

  ...
</member>