Caused by: java.lang.NullPointerException
    at com.ssbbpeople.metallurgy.blocks.grinder.ContainerGrinder.<init>(ContainerGrinder.java:211) ~[ContainerGrinder.class:?]
    at com.ssbbpeople.metallurgy.ModGuiHandler.getServerGuiElement(ModGuiHandler.java:21) ~[ModGuiHandler.class:?]
    at com.ssbbpeople.metallurgy.ModGuiHandler.getServerGuiElement(ModGuiHandler.java:1) ~[ModGuiHandler.class:?]
    at net.minecraftforge.fml.common.network.NetworkRegistry.getRemoteGuiContainer(NetworkRegistry.java:253) ~[NetworkRegistry.class:?]
    at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.openGui(FMLNetworkHandler.java:88) ~[FMLNetworkHandler.class:?]
    at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2809) ~[EntityPlayer.class:?]
    at com.ssbbpeople.metallurgy.blocks.grinder.Grinder.onBlockActivated(Grinder.java:55) ~[Grinder.class:?]
    at net.minecraft.server.management.PlayerInteractionManager.processRightClickBlock(PlayerInteractionManager.java:475) ~[PlayerInteractionManager.class:?]
    at net.minecraft.network.NetHandlerPlayServer.processTryUseItemOnBlock(NetHandlerPlayServer.java:769) ~[NetHandlerPlayServer.class:?]
    at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.processPacket(CPacketPlayerTryUseItemOnBlock.java:68) ~[CPacketPlayerTryUseItemOnBlock.class:?]
    at net.minecraft.network.play.client.CPacketPlayerTryUseItemOnBlock.processPacket(CPacketPlayerTryUseItemOnBlock.java:13) ~[CPacketPlayerTryUseItemOnBlock.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_221]
    at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_221]
    at net.minecraft.util.Util.runTask(Util.java:53) ~[Util.class:?]
    ... 5 more