Add ItemMapEmpty for diff visibility

src/main/java/net/minecraft/server/ItemMapEmpty.java

@@ -0,0 +1,34 @@
+package net.minecraft.server;
+
+public class ItemMapEmpty extends ItemWorldMapBase {
+
+    protected ItemMapEmpty(int i) {
+        super(i);
+        this.a(CreativeModeTab.f);
+    }
+
+    public ItemStack a(ItemStack itemstack, World world, EntityHuman entityhuman) {
+        ItemStack itemstack1 = new ItemStack(Item.MAP, 1, world.b("map"));
+        String s = "map_" + itemstack1.getData();
+        WorldMap worldmap = new WorldMap(s);
+
+        world.a(s, (WorldMapBase) worldmap);
+        worldmap.scale = 0;
+        int i = 128 * (1 << worldmap.scale);
+
+        worldmap.centerX = (int) (Math.round(entityhuman.locX / (double) i) * (long) i);
+        worldmap.centerZ = (int) (Math.round(entityhuman.locZ / (double) i) * (long) i);
+        worldmap.map = (byte) world.worldProvider.dimension;
+        worldmap.c();
+        --itemstack.count;
+        if (itemstack.count <= 0) {
+            return itemstack1;
+        } else {
+            if (!entityhuman.inventory.pickup(itemstack1.cloneItemStack())) {
+                entityhuman.drop(itemstack1);
+            }
+
+            return itemstack;
+        }
+    }
+}