fixed empty element template match

tried matching an xml doc:

    <param>
      <name>XXX</name>
      <value/>
    </param>

with template:


    `{{<param>
        <name>$_</name>
        <value>$0</value>
      </param>}}`

gives back an empty result

fixed to return <code>{ ['XXX'] = '' }</code>