texmath-0.12.9: test/writer/mml/mfencedAempty.test

<<< native
[ EGrouped [ EIdentifier "x" , EIdentifier "y" ]
, EMathOperator ""
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mrow>
      <mi>x</mi>
      <mi>y</mi>
    </mrow>
    <mi></mi>
    <mo>&#8289;</mo>
  </mrow>
</math>