Patch for entity_reference_revisions needed to delete subscriptions

A tidbit of information - in case in helps anyone else.

I was getting WSOD in trying to delete subscriptions - and this patch get it working.

https://www.drupal.org/project/entity_reference_revisions/issues/3320825 →

It's related to a core patch that I'd had to install as well ( https://www.drupal.org/node/2915972 → ). I'm not sure if this is common or not.