Minor code DRY-ing + subtle bug fix.

* DRYed up a code check pattern which exposed a subtle bug
  setting dsr[2] (start-tag-width) for nowiki spans.
* No change in parser test results but diffs exist where the new
  patch sets dsr[2] for nowiki spans instead of leaving them null.

Change-Id: I05bc5e04b9597a1c55d26ac54a650109f962bf65