Bukkit

What steps will reproduce the problem?
1. launch cauldron 1.7.10 server
2. get SEVERE error - null uid
3.

What is the expected output? What do you see instead?
No errors

What version of the product are you using?
zPermissions v1.3-SNAPSHOT
Cauldron server: Cauldron-MCPC-Plus-1.7.10-1.1179.03.105

Do you have an error log of what happened?
see below

Please provide any additional information below.

9:11:15 PM [SEVERE] Could not pass event AsyncPlayerPreLoginEvent to zPermissions v1.3-SNAPSHOT
9:11:15 PM org.bukkit.event.EventException
9:11:16 PM     at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:330) ~[JavaPluginLoader$1.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[RegisteredListener.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:30) ~[TimedRegisteredListener.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [SimplePluginManager.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:484) [SimplePluginManager.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at net.minecraft.server.network.ThreadPlayerLookupUUID.fireLoginEvents(ThreadPlayerLookupUUID.java:100) [ThreadPlayerLookupUUID.class:?]
9:11:16 PM     at net.minecraft.server.network.ThreadPlayerLookupUUID.run(ThreadPlayerLookupUUID.java:49) [ThreadPlayerLookupUUID.class:?]
9:11:16 PM Caused by: java.lang.IllegalArgumentException: uuid cannot be null
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.util.uuid.MojangUuidResolver.preload(MojangUuidResolver.java:112) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.listener.ZPermissionsPlayerListener.onAsyncPlayerPreLogin(ZPermissionsPlayerListener.java:60) ~[?:?]
9:11:16 PM     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_51]
9:11:16 PM     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_51]
9:11:16 PM     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_51]
9:11:16 PM     at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_51]
9:11:16 PM     at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:328) ~[JavaPluginLoader$1.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     ... 6 more
9:11:16 PM [INFO] UUID of player Dad_Yoshi is 20283bdf-2a61-42ba-87a5-6a6208498006
9:11:16 PM [WARNING] [zPermissions] Task #37 for zPermissions v1.3-SNAPSHOT generated an exception
9:11:16 PM java.lang.IllegalArgumentException: uuid cannot be null
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.dao.BaseMemoryPermissionDao.checkNameUuid(BaseMemoryPermissionDao.java:857) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.dao.BaseMemoryPermissionDao.getEntity(BaseMemoryPermissionDao.java:151) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.dao.BaseMemoryPermissionDao.updateDisplayName(BaseMemoryPermissionDao.java:753) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.dao.AvajePermissionDao2.updateDisplayName(AvajePermissionDao2.java:192) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.ZPermissionsPlugin$6$1.doInTransactionWithoutResult(ZPermissionsPlugin.java:1430) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.util.transaction.TransactionCallbackWithoutResult.doInTransaction(TransactionCallbackWithoutResult.java:30) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.util.transaction.AsyncTransactionStrategy.execute(AsyncTransactionStrategy.java:76) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.util.transaction.AsyncTransactionStrategy.execute(AsyncTransactionStrategy.java:59) ~[?:?]
9:11:16 PM     at org.tyrannyofheaven.bukkit.zPermissions.ZPermissionsPlugin$6.run(ZPermissionsPlugin.java:1427) ~[?:?]
9:11:16 PM     at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftTask.run(CraftTask.java:58) ~[CraftTask.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345) [CraftScheduler.class:git-Cauldron-MCPC-Plus-1.7.10-1.1179.03.105]
9:11:16 PM     at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:866) [MinecraftServer.class:?]
9:11:16 PM     at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:419) [lt.class:?]
9:11:16 PM     at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:806) [MinecraftServer.class:?]
9:11:16 PM     at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:666) [MinecraftServer.class:?]
9:11:16 PM     at java.lang.Thread.run(Unknown Source) [?:1.7.0_51]

This is a bug or misconfiguration in your server (Cauldron-MCPC-Plus). I would raise the issue with them.

Relevant event handler in zPerms:

    @EventHandler(priority=EventPriority.MONITOR)
    public void onAsyncPlayerPreLogin(AsyncPlayerPreLoginEvent event) {
        if (event.getLoginResult() == AsyncPlayerPreLoginEvent.Result.ALLOWED) {
            // Update display name
            core.updateDisplayName(event.getUniqueId(), event.getName());
        }
    }

AsyncPlayerPreLoginEvent.getUniqueId() is returning null. It should never be null.