[16:16:50 ERROR]: Encountered an unexpected exception
java.lang.NullPointerException
at com.mojang.authlib.GameProfile.hashCode(GameProfile.java:90) ~[minecraft_server.14w07a.jar:?]
at java.util.WeakHashMap.hash(Unknown Source) ~[?:1.7.0_51]
at java.util.WeakHashMap.put(Unknown Source) ~[?:1.7.0_51]
at org.apache.commons.lang3.builder.ToStringStyle.register(ToStringStyle.java:191) ~[minecraft_server.14w07a.jar:?]
at org.apache.commons.lang3.builder.ToStringStyle.appendClassName(ToStringStyle.java:1453) ~[minecraft_server.14w07a.jar:?]
at org.apache.commons.lang3.builder.ToStringStyle.appendStart(ToStringStyle.java:378) ~[minecraft_server.14w07a.jar:?]
at org.apache.commons.lang3.builder.ToStringBuilder.<init>(ToStringBuilder.java:263) ~[minecraft_server.14w07a.jar:?]
at org.apache.commons.lang3.builder.ToStringBuilder.<init>(ToStringBuilder.java:226) ~[minecraft_server.14w07a.jar:?]
at com.mojang.authlib.GameProfile.toString(GameProfile.java:97) ~[minecraft_server.14w07a.jar:?]
at ov.d(SourceFile:102) ~[minecraft_server.14w07a.jar:?]
at ov.a(SourceFile:93) ~[minecraft_server.14w07a.jar:?]
at ok.c(SourceFile:130) ~[minecraft_server.14w07a.jar:?]
at net.minecraft.server.MinecraftServer.v(SourceFile:555) ~[minecraft_server.14w07a.jar:?]
at nb.v(SourceFile:264) ~[minecraft_server.14w07a.jar:?]
at net.minecraft.server.MinecraftServer.u(SourceFile:471) ~[minecraft_server.14w07a.jar:?]
at net.minecraft.server.MinecraftServer.run(SourceFile:387) [minecraft_server.14w07a.jar:?]
at mr.run(SourceFile:657) [minecraft_server.14w07a.jar:?]

this happened on my server