Fix issue calling `create_table_from_selectable()` on LotDeviceDescendants

Replace `None` by `Column()`

sqlalchemy_utils on a4154bd0809bc6bbf0c27d5f7c0f3f2872edd779
breaks using `None` as padding parameter needed to follow restriction:
"All selectables passed to CompoundSelect must have identical numbers of columns"

ereuse_devicehub/resources/lot/models.py

@@ -275,7 +275,7 @@ class LotDeviceDescendants(db.Model):
         LotDevice.device_id,
         _desc.c.id.label('parent_lot_id'),
         _ancestor.c.id.label('ancestor_lot_id'),
-        None
+        db.column('padding')  # foo column to have same nunber of columns on joined selects (union)
     ]).select_from(_ancestor).select_from(lot_device).where(db.text(descendants))
 
     # Components