Missing bundle property on entity of type node. in entity_extract_ids() (line 7721 of ../includes/common.inc).

I have a site that is using Apache Solr Attachments module and when I try to delete the attachments index (/admin/config/search/apachesolr/attachments/confirm/delete) I get an error:

EntityMalformedException: Missing bundle property on entity of type node. in entity_extract_ids() (line 7721 of ../includes/common.inc).

Currently using:
Drupal 7.26
Apache Solr Search 7.x-1.6
Apache Solr Attachments 7.x-1.3

I found a similar issue in the post-install community: https://drupal.org/comment/8480215#comment-8480215 but it doesn't mention Apache Solr Attachments.

Any ideas on how to fix this?