Infernal Mobs V5.2.3 errors

[12:47:34] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'im' in plugin InfernalMobs v5.2
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:647) ~[spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.PlayerConnection.handleCommand(PlayerConnection.java:1386) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1221) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_131]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_131]
	at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:748) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]
Caused by: java.lang.NoSuchMethodError: org.bukkit.entity.Player.getTargetBlock(Ljava/util/HashSet;I)Lorg/bukkit/block/Block;
	at io.hotmail.com.jacob_vejvoda.infernal_mobs.infernal_mobs.onCommand(infernal_mobs.java:2785) ~[?:?]
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot-1.12.1-20170809a.jar:git-Spigot-5340a52-27b8bf9]
	... 15 more