Change empty language string to None in tldr.py

Author: columbarius

tldr.py

@@ -162,6 +162,7 @@ def get_language_list():
         lambda x: x.split('_')[0],
         filter(lambda x: x != 'C', languages)
     ))
+    languages = [None if language == '' else language for language in languages]
     if DEFAULT_LANG is not None:
         try:
             languages.remove(DEFAULT_LANG)