RPCN: settings fixes

[Megamouse]

• Fix segfault in rpcn settings dialog that happens when the dialog is closed without having properly initialized its rpcn object
• Fix file access violation in rpcn_config when version is 1 and the file is adjusted. The file handle was still in use in that scope.
  This is a regression from @elad335 's additional file checks for windows. I'm not sure if this also causes other issues elsewhere.
• Set rpcn default version to 2 (not sure why it's still 1)