Fixed potential crashes

src/app.py

@@ -64,11 +64,15 @@ def on_message_creator(mqtt_: MQTT):
         msg_json = json.loads(body)
         if 'probability' not in msg_json:
             logging.error("Malformed message from broker")
+            return
+
         if msg_json['probability'] > 0.5:
             r = requests.get(f"http://{config.INPUT_HOSTNAME}/sample/{msg_json['tag']}")
             r.raise_for_status()
             if 'device_id' not in r.json():
                 logging.error("Input-service response invalid")
+                return
+
             logging.info(f"Sending alert command to device {r.json()['device_id']}")
             mqtt_.publish(subtopic=r.json()['device_id'],
                           message=json.dumps({"command": "doAlert"}))