Continue Flask migration.

thermostat.py

@@ -132,6 +132,8 @@ def get_metric(metric, current_time, interval):
 def get_forced_mode():
   with app.app_context():
     row = db.session.execute(db.select(Set_mode.value, Set_mode.timestamp)).first()
+  if row is None:
+    return None
   #cur.execute("SELECT value, timestamp FROM set_mode WHERE name='mode'")
   #row = cur.fetchone()
   data = dict(zip(['value', 'timestamp'], row))