Add handler-case for client-reader: sb-bsd-sockets:not-connected-error
Add handler-case for client-reader: sb-bsd-sockets:not-connected-error

In some conditions this is signaled on server, like a abrupt disconnection
on the client. This make sure the client will be deleted and the error
will be handled.

ryukinix/lisp-chat,ryukinix/lisp-chat