When reading a property, if the projector returns a value which does not correspond to one in our tables, log a warning and return the raw ascii code instead of a KeyError
On init, try to validate the connection via the nullcmd. If no response from projector after max_retries, then log a warning, but don't abort initialisation, as the projector may become available later (could be powered off at wall).
KeyErrornullcmd. If no response from projector aftermax_retries, then log a warning, but don't abort initialisation, as the projector may become available later (could be powered off at wall).