improve learning if db is None (#513)

do not try to access self.db if we do not have a db_uri defined

closes #512

assume/common/outputs.py

@@ -169,6 +169,8 @@ def delete_similar_runs(self):
         """
         Deletes all similar runs from the database based on the simulation ID. This ensures that we overwrite simulations results when restarting one. Please note that a simulation which you also want to keep need to be assigned anew ID.
         """
+        if self.db_uri is None:
+            return
         query = text("select distinct simulation from rl_params")
 
         try:
@@ -684,9 +686,11 @@ def get_sum_reward(self):
         query = text(
             f"select unit, SUM(reward) FROM rl_params where simulation='{self.simulation_id}' GROUP BY unit"
         )
-        if self.db is not None:
-            with self.db.begin() as db:
-                rewards_by_unit = db.execute(query).fetchall()
+        if self.db is None:
+            return []
+
+        with self.db.begin() as db:
+            rewards_by_unit = db.execute(query).fetchall()
 
         # convert into a numpy array
         rewards_by_unit = [r[1] for r in rewards_by_unit]