unhandled enet errors if the network interface is shutdown

[elexis]

A sudo ifconfig eth0 down results in

ERROR: CNetServerWorker: enet_host_service failed (-1)

Then the server doesn't respond to anyone anymore.

Instead the error should be caught and it seems the hosting could still go on if the affected clients were disconnected.

We also get this one:

sendto: Network is unreachable

Alternatively these events should lead to some message box or closing of the page rather than going unnoticed.