It appears that a regression in commit 35c58e9 introduced the potential for an NPE when calling getPluralAttributes for a model without plural attributes. The method checks if declaredAttributes is null, but should likely check declaredPluralAttributes instead.
Please note that the opened PR targets the 5.4 branch. I can replace with a different PR if that is not correct.
many thanks! Yes we normally expert PRs to target master, but no worries I’l amend it.