SCServer does not handle disconnected client

[Sander van Dijk]

When a client disconnects, the server crashes with:

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> >'
  what(): write: Broken pipe
Aborted (core dumped)

This should be caught, and connection should be closed gracefully.