Fix possible crasher in WTS (only for commandline use of parse.js)

* The following command crashed the WTS because this doesn't
  provide any data-parsoid to WTS.

echo "<dl><dt>a</dt><dd>b</dd></dl>" | node parse --html2wt

Change-Id: I5130933383065e5177305919341285629b3fbd3c
Merge "Fix possible crasher in WTS (only for commandline use of parse.js)"