Upon receiving a null reference the plugin preceded to keep sending continuous error messages every millisecond can a fix be applied, please.

This is the whole message.

(00:15:30) | NullReferenceException

Found out what happened this is the first time he loaded the plugin on to his server upon him loading it the plugin tried to search the directory of all players that are online who are muted as well as offline players but it can't mute offline players so the plugin managed to crash the server because it's being informed I must mute these people but they don't exist because they're not online can a fix be applied, please.

Please check your logs for the full error.

that was the full error strangely enough

That wouldn't be the full error. The full error you can find in either oxide/logs or your server's output_log.txt set via -logfile.