Worldborder add shows an error with negative values

[NeunEinser]

The command worldborder add n with n < 0 is correct command syntax, however, the plugin shows an error, saying only values between positive 1 and 60,000,000 are allowed.
This may be true for the set command, the add command supports the range -60000000..60000000 though (-60000000 will never succeed, since during runtime the size cannot be below 1, it is still correct syntax though and the function file will load)

[NeunEinser]

moved to SpyglassMC/Spyglass#483