Can't use Saplings to create custom Trees

[Maurice Hülsevoort]

[04:33:16 INFO]: [EpicWorldGenerator] Biome mesa will not be generated.
[04:33:16 INFO]: [EpicWorldGenerator] Biome plains will not be generated.
[04:33:16 INFO]: [EpicWorldGenerator] Biome desert will not be generated.
[04:33:16 INFO]: [EpicWorldGenerator] Biome stone forest will not be generated.
[04:33:16 INFO]: CUSTOM TERRAIN: Scots pine forest
[04:33:16 WARN]: java.lang.ClassCastException: com.minelazz.epicworldgenerator.nativeAPI.implementations.v1_10_R1.generator.b cannot be cast to com.minelazz.epicworldgenerator.nativeAPI.implementations.v1_10_R1.generator.b
[04:33:16 WARN]:    at com.minelazz.epicworldgenerator.nativeAPI.implementations.v1_10_R1.NMSImplementation.a(NMSImplementation.java:203)
[04:33:16 WARN]:    at com.minelazz.epicworldgenerator.API.EpicAPI.a(EpicAPI.java:39)
[04:33:16 WARN]:    at com.minelazz.epicworldgenerator.EpicWorldGenerator.a(EpicWorldGenerator.java:454)
[04:33:16 WARN]:    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[04:33:16 WARN]:    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[04:33:16 WARN]:    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[04:33:16 WARN]:    at java.lang.reflect.Method.invoke(Method.java:497)
[04:33:16 WARN]:    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306)
[04:33:16 WARN]:    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
[04:33:16 WARN]:    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502)
[04:33:16 WARN]:    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.ItemStack.placeItem(ItemStack.java:138)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.PlayerInteractManager.a(PlayerInteractManager.java:532)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.PlayerConnection.a(PlayerConnection.java:890)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.PacketPlayInUseItem.a(SourceFile:55)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.PacketPlayInUseItem.a(SourceFile:11)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.PlayerConnectionUtils$1.run(SourceFile:13)
[04:33:16 WARN]:    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[04:33:16 WARN]:    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.SystemUtils.a(SourceFile:45)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:733)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:399)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:672)
[04:33:16 WARN]:    at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:571)
[04:33:16 WARN]:    at java.lang.Thread.run(Thread.java:745)
[04:33:16 ERROR]: Could not pass event StructureGrowEvent to EpicWorldGenerator v7.2.14
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.ItemStack.placeItem(ItemStack.java:138) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.PlayerInteractManager.a(PlayerInteractManager.java:532) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.PlayerConnection.a(PlayerConnection.java:890) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.PacketPlayInUseItem.a(SourceFile:55) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.PacketPlayInUseItem.a(SourceFile:11) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.PlayerConnectionUtils$1.run(SourceFile:13) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_51]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_51]
at net.minecraft.server.v1_10_R1.SystemUtils.a(SourceFile:45) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:733) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:399) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:672) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:571) [craftbukkit.jar:git-Spigot-c3e4052-1953f52]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_51]
Caused by: java.lang.NullPointerException
at com.minelazz.epicworldgenerator.API.EpicAPI.a(EpicAPI.java:40) ~[?:?]
at com.minelazz.epicworldgenerator.EpicWorldGenerator.a(EpicWorldGenerator.java:454) ~[?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_51]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_51]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_51]
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_51]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[craftbukkit.jar:git-Spigot-c3e4052-1953f52]
... 17 more

[Maurice Hülsevoort]

This happens whenever a player tries to use/grow a tree with a sapling. EWG-Trees won't generate, whenever someone tries only vanilla ones grow.