[CommonHTML] semantic tag causes shrink-wrapping of labels

The following gets shrink-wrapped:

<math>
  <semantics>
    <mtable>
      <mlabeledtr>
        <mtd><mtext>(1)</mtext></mtd>
        <mtd><mtext>Hello</mtext></mtd>
      </mlabeledtr>
    </mtable>
  </semantics>
</math>

If the semantics tag is removed, the rendering is correct.