From when I updated the server to the latest build on 13th September 2016 until now, every time the server tries to save the world (five minute auto save, save-all command, server stop), an Illegal Argument Exception is thrown. The world still seems to save okay but this error is flooding my console every five minutes and makes me concerned about the integrity of the save.

{{11:29:35 [warning] java.lang.IllegalArgumentException: Name and ID cannot both be blank
11:29:35 [warning] at com.mojang.authlib.GameProfile.<init>(GameProfile.java:25)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.UserCache.a(UserCache.java:90)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.UserCache.getProfile(UserCache.java:157)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.Village.b(Village.java:444)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.PersistentVillage.b(SourceFile:228)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.PersistentCollection.a(PersistentCollection.java:97)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.PersistentCollection.a(PersistentCollection.java:82)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.WorldServer.a(WorldServer.java:1071)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.WorldServer.save(WorldServer.java:1013)
11:29:35 [warning] at org.bukkit.craftbukkit.v1_10_R1.CraftWorld.save(CraftWorld.java:744)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:693)
11:29:35 [warning] at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:567)
11:29:35 [warning] at java.lang.Thread.run(Unknown Source)
}}