this is the server log tell me whats wrong I cant figure out
(NameReferencingFileConverter.java:409) [minecraft_server.jar:git-Spigot-596221b-9a1fc1e]
at net.minecraft.server.v1_12_R1.DedicatedServer.aS(DedicatedServer.java:630) [minecraft_server.jar:git-Spigot-596221b-9a1fc1e]
at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.java:223) [minecraft_server.jar:git-Spigot-596221b-9a1fc1e]
at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:544) [minecraft_server.jar:git-Spigot-596221b-9a1fc1e]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]
[21:22:38] [Server thread/WARN]: **** DETECTED OLD PLAYER DIRECTORY IN THE WORLD SAVE
[21:22:38] [Server thread/WARN]: **** THIS USUALLY HAPPENS WHEN THE AUTOMATIC CONVERSION FAILED IN SOME WAY
[21:22:38] [Server thread/WARN]: ** please restart the server and if the problem persists, remove the directory './world/players'
[21:22:38] [Server thread/INFO]: Stopping server
[21:22:38] [Server thread/INFO]: Saving players