fix default value for go

speciesData.py

@@ -49,10 +49,12 @@ class SpeciesData:
 
     def set_service_attribute(self, service, parameters_dictionary):
         parameters_dictionary_services = parameters_dictionary[constants.ORG_PARAM_SERVICES]
-        if(service in parameters_dictionary_services.keys() and parameters_dictionary_services[service] != ""):
-            return parameters_dictionary_services[service]
-        else:
-            return "0"
+        service_value = "0"
+        if(service in parameters_dictionary_services.keys()
+                and parameters_dictionary_services[service] is not None
+                and parameters_dictionary_services[service] != ""):
+            service_value = parameters_dictionary_services[service]
+        return service_value
 
     def __init__(self, parameters_dictionary):
         self.parameters_dictionary = parameters_dictionary