/island commands sometimes fail and throw NullPointerExceptions

[wesley27]

_Please paste the output from /usb version below: https://i.gyazo.com/66706bafba41c6540a0891171534b4aa.png

What steps will reproduce the problem?

1. Typing /is level or a similar command for another player, such as /is info
2. An error isn't thrown every time. Sometimes it works. Sometimes it fails and throws a NullPointerException. Then a couple seconds later it may work again. It's seemingly random.

_If you have any log-files, please paste them to pastebin.com: Server Log: https://pastebin.com/JyEa81sH In-Game chat corresponding to that server log: https://pastebin.com/2DsGduz7