Don't error when adding processors to NullExtent, simply do nothing (#1654)

worldedit-core/src/main/java/com/fastasyncworldedit/core/extent/NullExtent.java

@@ -219,6 +219,16 @@ public class NullExtent extends FaweRegionExtent implements IBatchProcessor {
         throw reason;
     }
 
+    @Override
+    public Extent addProcessor(final IBatchProcessor processor) {
+        return this;
+    }
+
+    @Override
+    public Extent addPostProcessor(final IBatchProcessor processor) {
+        return this;
+    }
+
     @Override
     public BlockArrayClipboard lazyCopy(Region region) {
         throw reason;