Error

[20:48:53] [Server thread/ERROR] [net.minecraft.entity.EntityTracker]: "Silently" catching entity tracking error.
net.minecraft.util.ReportedException: Adding entity to track
	at net.minecraft.entity.EntityTracker.track(EntityTracker.java:261) [EntityTracker.class:?]
	at net.minecraft.entity.EntityTracker.track(EntityTracker.java:103) [EntityTracker.class:?]
	at net.minecraft.world.ServerWorldEventHandler.onEntityAdded(ServerWorldEventHandler.java:43) [ServerWorldEventHandler.class:?]
	at net.minecraft.world.World.onEntityAdded(World.java:1325) [World.class:?]
	at net.minecraft.world.WorldServer.onEntityAdded(WorldServer.java:1175) [WorldServer.class:?]
	at net.minecraft.world.World.spawnEntity(World.java:1316) [World.class:?]
	at net.minecraft.world.WorldServer.spawnEntity(WorldServer.java:1121) [WorldServer.class:?]
	at com.btrthnu.guns.objects.item.base.GunBase.shootGun(GunBase.java:287) [GunBase.class:?]
	at com.btrthnu.guns.objects.item.GunAimable.onItemRightClick(GunAimable.java:53) [GunAimable.class:?]
	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:234) [ItemStack.class:?]
	at net.minecraft.server.management.PlayerInteractionManager.processRightClick(PlayerInteractionManager.java:384) [PlayerInteractionManager.class:?]
	at net.minecraft.network.NetHandlerPlayServer.processTryUseItem(NetHandlerPlayServer.java:794) [NetHandlerPlayServer.class:?]
	at net.minecraft.network.play.client.CPacketPlayerTryUseItem.processPacket(CPacketPlayerTryUseItem.java:43) [CPacketPlayerTryUseItem.class:?]
	at net.minecraft.network.play.client.CPacketPlayerTryUseItem.processPacket(CPacketPlayerTryUseItem.java:9) [CPacketPlayerTryUseItem.class:?]
	at net.minecraft.network.PacketThreadUtil$1.run(PacketThreadUtil.java:21) [PacketThreadUtil$1.class:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_201]
	at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_201]
	at net.minecraft.util.Util.runTask(Util.java:53) [Util.class:?]
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:798) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:743) [MinecraftServer.class:?]
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:192) [IntegratedServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:592) [MinecraftServer.class:?]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_201]
Caused by: java.lang.IllegalArgumentException: Don't know how to add class com.btrthnu.guns.objects.item.entity.EntityBullet!
	at net.minecraft.entity.EntityTrackerEntry.createSpawnPacket(EntityTrackerEntry.java:681) ~[EntityTrackerEntry.class:?]
	at net.minecraft.entity.EntityTrackerEntry.updatePlayerEntity(EntityTrackerEntry.java:399) ~[EntityTrackerEntry.class:?]
	at net.minecraft.entity.EntityTrackerEntry.updatePlayerEntities(EntityTrackerEntry.java:509) ~[EntityTrackerEntry.class:?]
	at net.minecraft.entity.EntityTracker.track(EntityTracker.java:235) ~[EntityTracker.class:?]