Merge pull request #47 from 2bndy5/master

payload parameter of type `None` replaced with zero-length string in `will_set()`

Author: brentru

adafruit_minimqtt/adafruit_minimqtt.py

@@ -217,7 +217,7 @@ def will_set(self, topic=None, payload=None, qos=0, retain=False):
         if self._is_connected:
             raise MMQTTException("Last Will should only be called before connect().")
         if payload is None:
-            raise MMQTTException("Message can not be None.")
+            payload = ""
         if isinstance(payload, (int, float, str)):
             payload = str(payload).encode()
         else: