Updated for Bukkit changes.

src/main/java/com/sk89q/worldedit/LocalWorld.java

@@ -316,4 +316,13 @@ public abstract class LocalWorld {
      */
     @Override
     public abstract int hashCode();
+
+    /**
+     * Get the world's height
+     * 
+     * @return
+     */
+    public int getHeight() {
+        return 127;
+    }
 }

src/main/java/com/sk89q/worldedit/bukkit/BukkitWorld.java

@@ -699,4 +699,9 @@ public class BukkitWorld extends LocalWorld {
     public int hashCode() {
         return world.hashCode();
     }
+
+    @Override
+    public int getHeight() {
+        return world.getMaxHeight() - 1;
+    }
 }

src/main/java/com/sk89q/worldedit/bukkit/EditSessionBlockChangeDelegate.java

@@ -56,4 +56,8 @@ public class EditSessionBlockChangeDelegate implements BlockChangeDelegate {
     public int getTypeId(int x, int y, int z) {
         return editSession.getBlockType(new Vector(x, y, z));
     }
+
+    public int getHeight() {
+        return editSession.getWorld().getHeight();
+    }
 }