ndp spoof: cannot disable neighbor advertisements

[konradh]

The description of the ndp.spoof.neighbour option states that I can disable neighbor advertisements by clearing the option. Because this option has an IPv6Validator set, this is not possible.

Steps to Reproduce

bettercap v2.32.0 (built for linux amd64 with go1.21.6) [type 'help' for a list of commands]
...
  » set ndp.spoof.neighbour ''
  » set ndp.spoof.targets 2001:db8::42
  » ndp.spoof on
  » [19:45:11] [sys.log] [err] Parameter ndp.spoof.neighbour not valid: '' does not match rule '^[:a-fA-F0-9]{6,}$'.

Expected behavior: ndp.spoof on does not produce an error and no neighbor advertisements are sent.

Actual behavior: ndp.spoof on produces an error.