Merge pull request #6 from margaret/issue_5

Add check that data[0] is not None before trying to parse it

adafruit_gps.py

@@ -195,7 +195,7 @@ def _parse_gprmc(self, args):
         # Parse the arguments (everything after data type) for NMEA GPRMC
         # minimum location fix sentence.
         data = args.split(',')
-        if data is None or len(data) < 11:
+        if data is None or len(data) < 11 or data[0] is None:
             return  # Unexpected number of params.
         # Parse fix time.
         time_utc = int(_parse_float(data[0]))