/// api_version=2
var script = registerScript({
	name: "EpicFail",
	version: "2.0",
	authors: ["OrangeCat", "Katchum"]
});
var prf = ", "+script.scriptName + " v"+script.scriptVersion+ " by";
Java.type("java.util.Arrays").asList(script.scriptAuthors).forEach(function(e){
	prf += (e != script.scriptAuthors[0] ? ", " : " ") + e;
});
script.registerModule({
	name: script.scriptName,
	description: "tf" + prf,
	category: "Movement",
	tag: "sigma"
}, function (module) {
	var GuiChest = Java.type("net.minecraft.client.gui.inventory.GuiChest");
	var ContainerChest = Java.type("net.minecraft.inventory.ContainerChest");
	var IInventory = Java.type("net.minecraft.inventory.IInventory");
	module.on("update", function(e){
		var cr = mc.currentScreen;
		var cry = mc.thePlayer.openContainer;
		if(cr != null && cr instanceof GuiChest){ // i fucking hate js
			var i = cr.lowerChestInventory;
			if(i instanceof IInventory){ // tf is this
				// get actual inventory is my method in java client, figure out how to get the correct inventory
				var rp = new (Java.extend(GuiChest))(mc.thePlayer.getActualInventory(), i){
					drawScreen: function(mouseX, mouseY, partialTicks){
						Chat.print("i forgor :skull:")
					}
				};
				var sc = mc.class.getDeclaredField("currentScreen");
				sc.setAccessible(true);
				sc.set(mc, rp);
			}
		}
	});
});

here is the stack trace thing:

aparently it makes the player null