Handle cancelled trains

[andrewjw]

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Exception occurred during processing of request from ('192.168.1.36', 52493)
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/socketserver.py", line 318, in _handle_request_noblock
    self.process_request(request, client_address)
  File "/usr/local/lib/python3.12/socketserver.py", line 349, in process_request
    self.finish_request(request, client_address)
  File "/usr/local/lib/python3.12/socketserver.py", line 362, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/local/lib/python3.12/socketserver.py", line 761, in __init__
    self.handle()
  File "/usr/local/lib/python3.12/http/server.py", line 436, in handle
    self.handle_one_request()
  File "/usr/local/lib/python3.12/http/server.py", line 424, in handle_one_request
    method()
  File "/display/smartdisplay/smart_display_handler.py", line 30, in do_GET
    data = self.trains_to_london()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/display/smartdisplay/smart_display_handler.py", line 132, in trains_to_london
    "trains": get_trains_to_london()
              ^^^^^^^^^^^^^^^^^^^^^^
  File "/display/smartdisplay/trains.py", line 64, in get_trains_to_london
    "is_late": _is_late(train.std, train.etd)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/display/smartdisplay/trains.py", line 106, in _is_late
    ehour, eminute = int(estimated.split(":")[0]), int(estimated.split(":")[1])
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: invalid literal for int() with base 10: 'Cancelled'
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