MythicMobs error with MPet

[11:39:46 FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.AssertionError: TRAP
        at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_162]
        at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_162]
        at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:47) [spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:748) [spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_162]
Caused by: java.lang.AssertionError: TRAP
        at net.minecraft.server.v1_12_R1.ItemStack.F(ItemStack.java:100) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.ItemStack.setCount(ItemStack.java:831) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.PlayerInteractManager.a(PlayerInteractManager.java:413) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1004) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:26) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:1) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at net.minecraft.server.v1_12_R1.PlayerConnectionUtils$1.run(SourceFile:13) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_162]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_162]
        at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) ~[spigot_server.jar:git-Spigot-7754231-a3b3a42]
        ... 5 more
[11:39:48 WARN]: [MythicMobs] ✗ Config Error for Mob 'TMP' in 'ExampleMobs.yml': Mob type may not be supported on this version of Minecraft. Enable debugging for more information.