text: Title: DHT22 unable to activate with daemon
  Body: ## Mycodo Issue Report:
    - Specific Mycodo Version: 7.4.3
   
  #### Problem Description
  Please list:
  
    - trying to add and activate DHT22 unit 
    - tested the unit seperately and works but seems to run into an error with the mycodo daemon
   
  ### Errors
  Error: Could not activate Input controller with ID 7829a1e3-f8bf-4430-a1e4-04ff0ed4c403: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
  
  
  DAEMON LOG
  
  2019-04-21 13:57:00,148 - mycodo.daemon - WARNING - Input controller with ID 7829a1e3-f8bf-4430-a1e4-04ff0ed4c403 not found
  2019-04-21 13:57:23,466 - mycodo.daemon - ERROR - Could not activate Input controller with ID 495f207f-ed95-4f2c-b9d6-3635ea7c4f0f: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
  Traceback (most recent call last):
    File "/var/mycodo-root/mycodo/mycodo_daemon.py", line 556, in controller_activate
      ready, cont_id)
    File "/var/mycodo-root/mycodo/controller_input.py", line 173, in __init__
      self.measure_input = input_loaded.InputModule(self.input_dev)
    File "/home/pi/Mycodo/mycodo/inputs/dht22.py", line 117, in __init__
      self.gpio = int(input_dev.gpio_location)
  TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
  
  from line; 
  
  https://github.com/kizniche/Mycodo/blob/b220ed6f04b9718653e6b8a77ca7f9a4a2e70811/mycodo/mycodo_daemon.py#L564-L569
  
  ### Steps to Reproduce the issue:
  How can this issue be reproduced?
   1. Add DHT to Mycodo using Setup > Data > Input dropdown > DHT22
   2. Activate DHT using the Activate button
   3. Error thrown up saying;
  > "Error: Could not activate Input controller with ID 495f207f-ed95-4f2c-b9d6-3635ea7c4f0f: int() argument must be a string, a bytes-like object or a number, not 'NoneType'