small tweak to clean() to show failure deatils

In json output, there was no detail shown for the failures.  Adding line #69 results in failed tests showing the 'err' object.
removing ' || undefined'
"Merge pull request #1205 from ben-bradley/patch-1\n\nsmall tweak to clean() to show failure deatils"

* ben-bradley/patch-1:
  removing ' || undefined'
  small tweak to clean() to show failure deatils
Fix style (#1205)