Connecting with netcat and sending non-JSON throws exception

[fidgetingbits]

May be worth fixing this so the server output is a bit cleaner when trying to diagnose other errors

Traceback (most recent call last):
  File "/home/edg/IDArling/idarling/shared/sockets.py", line 199, in _notify_read
    dct = json.loads(line.decode("utf-8"))
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)