User unable to post to WordPress

User reported in 1614639-zen that they have trouble publishing their posts to WordPress.com. I've noticed on the add-on page that most recent reviews are complaining about the same errors of not being able to post to WordPress.com.

##Steps they take
While in Google Docs they go to Add ons -> Publish to Wordpress.

##Expected result
Their post publishes on their WordPress.com site

##What actually happens
They receive two types of errors:
1. TypeError. Cannot read property 1 from null
2. We're sorry, a server error occurred. Please wait a bit and try again.

##Troubleshooting they have tried:
1. Disconnecting their blog and reconnecting it
2. Reinstalling the add on
3. Testing a different document with success, while another fails

Start at the Google Docs Add-ons → Publish to Wordpress entry point and reproduce the issue with both a document that succeeds and one that fails. Investigate the two reported errors, and consider the work done when the previously failing document publishes to WordPress.com without either error.

Written by the indexing model from the issue text.