[FIX] uom: fix nonempty reference constraint on uom categories

What's the deal with SQL queries?
The query in _check_category_reference_uniqueness returns:
category_id | uom_count
-------------+-----------
(0 rows)
but if we removed AND U.active = 't', we would have had:
category_id | uom_count
-------------+-----------
8 |         0
(1 row)
As a result, the check on uom_data['uom_count'] == 0 could simply never be true.

opw 1959679

closes odoo/odoo#32788

Signed-off-by: Nans Lefebvre (len) <len@odoo.com>

addons/uom/models/uom_uom.py

@@ -83,9 +83,8 @@ class UoM(models.Model):
         self._cr.execute("""
             SELECT C.id AS category_id, count(U.id) AS uom_count
             FROM uom_category C
-            LEFT JOIN uom_uom U ON C.id = U.category_id AND uom_type = 'reference'
+            LEFT JOIN uom_uom U ON C.id = U.category_id AND uom_type = 'reference' AND U.active = 't'
             WHERE C.id IN %s
-                AND U.active = 't'
             GROUP BY C.id
         """, (tuple(category_ids),))
         for uom_data in self._cr.dictfetchall():

addons/uom/tests/test_uom.py

@@ -68,6 +68,16 @@ class TestUom(TransactionCase):
             'name': 'Custom UoM category',
         })
 
+        # at first we can not create a non reference in custom category
+        with self.assertRaises(ValidationError):
+            self.env['uom.uom'].create({
+                'name': 'Bigger UoM of my category',
+                'factor_inv': 42,
+                'uom_type': 'bigger',
+                'rounding': 0.5,
+                'category_id': category.id
+            })
+
         # create the reference
         self.env['uom.uom'].create({
             'name': 'Reference UoM of my category',