Fixes #97: Return proper json in xmlToJson method, for none data arguments.

Previously our xmlToJson method returns ' ' on None argument,
which is not proper json data.
We should return '[]' for None data, instead ' '.

This commit change the default value of resultant json data.

Author: YJDave

loklak.py

@@ -74,7 +74,7 @@ def status(self):
 
     def xmlToJson(self, xmlData = None):
         """Convert XML to JSON as the service."""
-        jsonData = ''
+        jsonData = '[]'
         if xmlData:
             jsonData = dumps(bf.data(et.fromstring(xmlData)))
         return jsonData