Fix post_update hook error when quantities have multiple revisions.
Example error:
[error] SQLSTATE[21000]: Cardinality violation: 7 ERROR: more than one row returned by a subquery used as an expression: UPDATE "quantity_revision" qr SET value__numerator = (SELECT unit_quantity_numerator FROM "quantity_revision__unit_quantity" uq WHERE uq.entity_id = qr.id), value__denominator = (SELECT unit_quantity_denominator FROM "quantity_revision__unit_quantity" uq WHERE uq.entity_id = qr.id) WHERE qr.id = :id; Array