[2.0.60] Crash when using --enable-lua-udp on port already in use and mod calls send_udp

[longuint]

• What did you do?
  Started Factorio with --enable-lua-udp and specified a port already occupied by another process. A mod then called send_udp on that same port.
• What happened?
  The game crashed immediately when the mod executed send_udp.
• What did you expect to happen instead?
  I expected an error or exception in the mod API, or for the packet to fail silently, rather than crashing the entire game.
• How often does this happen?
  Always reproducible when the same conditions are met.
  
  Reproduction Steps:
  Run nc -u -l 5000 (or similar) to occupy UDP port 5000.
  Start Factorio with --enable-lua-udp=5000.
  Use a mod that calls send_udp on port 5000.
  Observe the crash.

[Rseding91]

Thanks for the report. This is now fixed for the next release.