Crash when canceling missed transaction

When canceling a missed transaction, it crash:

mjaEkdjxWLeENQtcfXm7iobqB49uT1Bgp3:409106529319839136\nComment: \nRX6FaVeWeuNVlf4iRKjZQgywFXfFt1M/gZZ4/UPep1RpAqTNg/Nrgw7mgLhLJ14Y+22+cVEJDI/w+Hg+BofEDg==\n'}
DEBUG:transfer:_try_transition:9BCE4 : TO_SEND --> AWAITING
DEBUG:toast:display:NOTIFY DISPLAY
DEBUG:community:get_block:Requesting block 1
Traceback (most recent call last):
  File "/home/moul/projects/sakia/build/src/sakia/gui/widgets/context_menu.py", line 88, in <lambda>
    cancel.triggered.connect(lambda checked, tr=transfer: menu.cancel_transfer(tr))
  File "/home/moul/projects/sakia/build/src/sakia/gui/widgets/context_menu.py", line 167, in cancel_transfer
    transfer.cancel()
  File "/home/moul/projects/sakia/build/src/sakia/core/transfer.py", line 326, in cancel
    self.run_state_transitions(())
  File "/home/moul/projects/sakia/build/src/sakia/core/transfer.py", line 318, in run_state_transitions
    if self._try_transition(key, inputs):
  File "/home/moul/projects/sakia/build/src/sakia/core/transfer.py", line 300, in _try_transition
    logging.debug("{0} : {1} --> {2}".format(self.sha_hash[:5], self.state.name,
TypeError: 'NoneType' object is not subscriptable