Hello, I have a big problem with Quests - it very often throws NullPointerException when player moves or in tasks.

Here are the stacktraces:

[15:42:44] [Server thread/ERROR]: Could not pass event PlayerMoveEvent to Quests v2.6.8-b109
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-db6de12-18fbb24]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:270) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.PacketPlayInFlying.a(SourceFile:126) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.PacketPlayInFlying$PacketPlayInPosition.a(SourceFile:57) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [spigot.jar:git-Spigot-db6de12-18fbb24]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_91]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_91]
at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:715) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot.jar:git-Spigot-db6de12-18fbb24]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot.jar:git-Spigot-db6de12-18fbb24]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_91]<

And:

[15:42:59] [Server thread/WARN]: [Quests] Task #521 for Quests v2.6.8-b109 generated an exception
java.lang.NullPointerException<

Thanks in advance ;)