fix duplication of same objects in db with when saving a child scenario

src/Model/Pollutants/Pollutants.py

@@ -400,7 +400,7 @@ class Pollutants(SQLSubModel):
             return new
 
         table = execute(
-            "SELECT pamhyr_id, deleted, name FROM pollutants " +
+            "SELECT pamhyr_id, deleted, name, scenario FROM pollutants " +
             f"WHERE scenario = {scenario.id} " +
             f"AND pamhyr_id NOT IN ({', '.join(map(str, loaded))})"
         )
@@ -412,10 +412,12 @@ class Pollutants(SQLSubModel):
                 pid = next(it)
                 deleted = (next(it) == 1)
                 name = next(it)
+                owner_scenario = next(it)
 
                 new_pollutant = cls(
                     id=pid, name=name,
-                    status=status
+                    status=status,
+                    owner_scenario=owner_scenario
                 )
                 if deleted:
                     new_pollutant.set_as_deleted()