cubicweb #7978475 datafeed does properly handle deletion of relation with cardinality 1 [open]

(real life from activite->crm datafeed)

Given the following piece of schema: Order (1) ---split_into---> (*) WorkOrder

If in the source a WorkOrder instance is deleted, upon source sync, datafeed does delete the split_into relation and commit before deleting the WorkOrder entity => crash

done in<not specified>
closed by<not specified>