AttributeError: 'NoneType' object has no attribute 'lower'

[erdoukki]

diff --git a/pylms/server.py b/pylms/server.py
index 3fe1a3e..e20583e 100644
--- a/pylms/server.py
+++ b/pylms/server.py
@@ -171,8 +171,8 @@ class Server(object):
         """
         if isinstance(ref, str):
             ref = self.__decode(ref)
-        ref = ref.lower()
         if ref:
+            ref = ref.lower()
             for player in self.players:
                 player_name = player.name.lower()
                 player_ref = player.ref.lower()