-fix outputs queries (#207)

small mistake prevents simulations from running when database is just
created

assume/common/outputs.py

@@ -357,11 +357,14 @@ async def on_stop(self):
         for query in queries:
             try:
                 df = pd.read_sql(query, self.db)
-            except OperationalError:
+            except (OperationalError, ProgrammingError):
                 continue
 
             dfs.append(df)
 
+        if not dfs:
+            return
+
         df = pd.concat(dfs)
         df.reset_index()
         df["simulation"] = self.simulation_id