Snapshot 18w21a crashing

23.05 11:23:24 [Multicraft] Not restarting crashed server. 23.05 11:23:24 [Disconnect] User VirtualWandering has disconnected, reason: Server shutting down 23.05 11:23:24 [Multicraft] Server stopped 23.05 11:23:24 [Multicraft] Server shut down 23.05 11:23:23 [Server] Server Shutdown Thread/INFO Saving players 23.05 11:23:23 [Server] Server Shutdown Thread/INFO Stopping server 23.05 11:23:22 [Server] Server thread/INFO Saving chunks for level 'Family Fun'/the_end 23.05 11:23:22 [Server] Server thread/INFO Saving chunks for level 'Family Fun'/the_nether 23.05 11:23:22 [Server] Server thread/INFO Saving chunks for level 'Family Fun'/overworld 23.05 11:23:22 [Server] Server thread/INFO Saving worlds 23.05 11:23:22 [Server] Server thread/INFO Saving players 23.05 11:23:22 [Server] Server thread/INFO Stopping server 23.05 11:23:22 [Server] Server thread/ERROR This crash report has been saved to: /./crash-reports/crash-2018-05-23_11.23.22-server.txt