Remove bad default copy method in AbstractMask

worldedit-core/src/main/java/com/sk89q/worldedit/function/mask/AbstractMask.java

@@ -19,21 +19,7 @@
 
 package com.sk89q.worldedit.function.mask;
 
-import org.jetbrains.annotations.Nullable;
-
 /**
  * A base class of {@link Mask} that all masks should inherit from.
  */
-public abstract class AbstractMask implements Mask {
-
-    @Override
-    @Nullable
-    public Mask copy() {
-        try {
-            return (Mask) super.clone();
-        } catch (CloneNotSupportedException e) {
-            return null;
-        }
-    }
-
-}
+public abstract class AbstractMask implements Mask {}