Don't log Quant unpublish errors when content is a 404

Ended up piggybacking off of this issue when I was debugging/testing:

https://github.com/quantcdn/drupal/pull/200

This will be merged into the Drupal.org repo in the next few days and included in the next release.

Automatically closed - issue fixed for 2 weeks with no activity.

Kristen Pol → credited steveworley → .

Adding attribution.

Part of 1.6.0 release → .