[21:39:31] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_66]
        at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_66]
        at net.minecraft.util.Util.func_181617_a(SourceFile:45) [g.class:?]
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:660) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:344) [ko.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:605) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:481) [MinecraftServer.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_66]
Caused by: java.lang.NullPointerException
        at net.minecraft.entity.passive.EntityWolf.onTame(SourceFile:87) ~[ua.class:?]
        at net.minecraft.entity.passive.EntityWolf.func_70085_c(SourceFile:348) ~[ua.class:?]
        at net.minecraft.entity.EntityLiving.func_130002_c(EntityLiving.java:980) ~[ps.class:?]
        at net.minecraft.entity.player.EntityPlayer.func_70998_m(EntityPlayer.java:1163) ~[wn.class:?]
        at net.minecraft.network.NetHandlerPlayServer.func_147340_a(NetHandlerPlayServer.java:884) ~[lm.class:?]
        at net.minecraft.network.play.client.C02PacketUseEntity.func_148833_a(SourceFile:52) ~[in.class:?]
        at net.minecraft.network.play.client.C02PacketUseEntity.func_148833_a(SourceFile:11) ~[in.class:?]
        at org.spongepowered.common.network.PacketUtil.onProcessPacket(PacketUtil.java:106) ~[PacketUtil.class:1.8.9-1694-3.1.0-BETA-1065]
        at net.minecraft.network.PacketThreadUtil$1.onProcessPacket(SourceFile:51) ~[fh$1.class:?]
        at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fh$1.class:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_66]
        at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_66]
        at net.minecraft.util.Util.func_181617_a(SourceFile:44) ~[g.class:?]
        ... 5 more