Bukkit

What steps will reproduce the problem?
1. Creating a storage minecart entity using any method, also during world generation process.

What is the expected output? What do you see instead?
It generates a storage minecart twice with an exception.

What version of the product are you using?
MinecartMania 2.6 for CB 1.7.9-R0.2 with Spigot 1.7.10

Do you have an error log of what happened?
[22:16:53 ERROR]: Could not pass event VehicleCreateEvent to MinecartMania v2.5
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.EntityMinecartAbstract.<init>(EntityMinecartAbstract.java:104) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.EntityMinecartContainer.<init>(EntityMinecartContainer.java:52) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.EntityMinecartChest.<init>(SourceFile:15) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.EntityMinecartAbstract.a(EntityMinecartAbstract.java:47) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.ItemMinecart.interactWith(ItemMinecart.java:25) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.ItemStack.placeItem(ItemStack.java:102) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.PlayerInteractManager.interact(PlayerInteractManager.java:391) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java:662) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.PacketPlayInBlockPlace.a(SourceFile:60) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.PacketPlayInBlockPlace.handle(SourceFile:9) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:184) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java:81) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:734) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:289) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
Caused by: java.lang.NullPointerException
        at org.bukkit.craftbukkit.v1_7_R4.inventory.CraftInventory.getContents(CraftInventory.java:57) ~[spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        at com.afforess.minecartmania.minecarts.MMMinecart.replaceCart(MMMinecart.java:1143) ~[?:?]
        at com.afforess.minecartmania.minecarts.MMMinecart.<init>(MMMinecart.java:64) ~[?:?]
        at com.afforess.minecartmania.minecarts.MMStorageCart.<init>(MMStorageCart.java:37) ~[?:?]
        at com.afforess.minecartmania.entity.MinecartManiaWorld.CreateMMMinecart(MinecartManiaWorld.java:84) ~[?:?]
        at com.afforess.minecartmania.listeners.CoreListener.onCreate(CoreListener.java:32) ~[?:?]
        at sun.reflect.GeneratedMethodAccessor304.invoke(Unknown Source) ~[?:?]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_25]
        at java.lang.reflect.Method.invoke(Method.java:483) ~[?:1.8.0_25]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:298) ~[spigot-1.7.10-R0.1-SNAPSHOT.jar:git-Spigot-1627]
        ... 20 more