Whitelist act as a blacklist

[m4rise]

I cannot use the whitelist feature.
Checked inside project, it seems the issue is related to not operator in isUserAllowed() method.

DiscordSoundboard/src/main/java/net/dirtydeeds/discordsoundboard/service/SoundPlayerImpl.java

Line 377 in f8b0aca

} else return !allowedUsers.contains(username);