ci: enable continuous integration

Signed-off-by: Thomas Klaehn <thomas.klaehn@u-blox.com>

source/data_buffer/__init__.py

@@ -13,7 +13,7 @@ class DataBuffer(object):
         return True
 
     def average(self):
-        if len(self.__data) != self.__max:
+        if len(self.__data) is 0:
             return None
         return sum(self.__data) / len(self.__data)