PrisonUtils error

[17:57:38] [Server thread/ERROR]: Could not pass event BlockBreakEvent to PrisonUtils v1.5.1
org.bukkit.event.EventException
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PlayerInteractManager.breakBlock(PlayerInteractManager.java:286) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PlayerInteractManager.a(PlayerInteractManager.java:189) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PlayerConnection.a(PlayerConnection.java:588) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PacketPlayInBlockDig.a(SourceFile:40) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PacketPlayInBlockDig.a(SourceFile:10) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.PacketHandleTask.run(SourceFile:13) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_25]
	at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_25]
	at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:683) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:316) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:623) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:526) [spigot.jar:git-Spigot-c46583f-e6f9fd4]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_25]
Caused by: java.lang.NullPointerException
	at me.mrCookieSlime.PrisonUtils.main$2$1.onSell(main.java:104) ~[?:?]
	at me.mrCookieSlime.QuickSell.Shop.sell(Shop.java:172) ~[?:?]
	at me.mrCookieSlime.PrisonUtils.MiningListener.handleMining(MiningListener.java:186) ~[?:?]
	at me.mrCookieSlime.PrisonUtils.MiningListener.onBlockBreak(MiningListener.java:122) ~[?:?]
	at sun.reflect.GeneratedMethodAccessor128.invoke(Unknown Source) ~[?:?]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_25]
	at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_25]
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot.jar:git-Spigot-c46583f-e6f9fd4]
	... 16 more