Fix return of account income.

accountant/views/accounts.py

@@ -300,9 +300,9 @@ class BalanceResource(Resource):
 
         data = range_parser.parse_args()
 
-        # Note: if we don't pass the code, the result is seen as a tuple and
-        # causes error on marshalling.
-        return account.income(**data), 200
+        return row_as_dict(
+            account.income(**data)
+        ), 200
 
 
 @ns.route("/<int:account_id>/category")