@unknown Yes, just tested with 1.13.1 and it still happens.
This is still an issue with 1.11.2, please reopen.
Cannot be. MC-79990 just shows usage of checkNotNull. This issue is caused by improper file handling of usercache.json, so definitely related to UUID lookup, maybe happens when the server is not stopped gracefully. This crash happens because the usercache.json file is completely empty instead of containing "[]" (empty array).
Deleting usercache.json fixes this.
Getting this on a dedicated 1.8.4 server as well.
@unknown: What they mean with "Won't fix" is that this is expected behavior by Mojang.
@unknown Can we actually get some insight about why this won't be fixed?
Asking for a re-open now that 21w37a has been released.