I also get the following error when previewing with NW JS:
in .. /html/ajax_plugin.js : process is not defined.
--- UPDATE ---
As a temporary fix, I reverted to 0.12.0 NW.JS from February. Works fine.
I have the same issue, it's been posted in the bugs forum by multple users. Thanks for the tip abpout reverting, wiill have to try that as a temp solution so I can keep working on things.