crash in become_target message handler

[Timtam]

Traceback (most recent call last):
File "/home/tyler/ygo/ygo-game/ygo/utils.py", line 116, in catch
return f(*args, **kwargs)
File "/home/tyler/ygo/ygo-game/ygo/duel.py", line 252, in process_messages
data = fn(data)
File "/home/tyler/ygo/ygo-game/ygo/message_handlers/become_target.py", line 13, in msg_become_target
self.cm.call_callbacks('become_target', tc, tl, tseq)
File "/home/tyler/ygo/ygo-game/ygo/callback_manager.py", line 20, in call_callbacks
callback(*args, **kwargs)
File "/home/tyler/ygo/ygo-game/ygo/message_handlers/become_target.py", line 20, in become_target
name = self.players[self.chaining_player].nickname
AttributeError: 'Duel' object has no attribute 'chaining_player'