Array splice should only normalize deleted_elements if it's an array

src/js/array.js

Index: src/js/array.js
diff --git a/src/js/array.js b/src/js/array.js
index 671e507a1568bed82f41a6b1f7040c6493e6c867..355f9962b63a3cab5ae5d2088dfad0fa06b891ad 100644
--- a/src/js/array.js
+++ b/src/js/array.js
@@ -729,7 +729,7 @@ function ArraySplice(start, delete_count) {
   }
   if (UseSparseVariant(array, len, IS_ARRAY(array), changed_elements)) {
     %NormalizeElements(array);
-    %NormalizeElements(deleted_elements);
+    if (IS_ARRAY(deleted_elements)) %NormalizeElements(deleted_elements);
     SparseSlice(array, start_i, del_count, len, deleted_elements);
     SparseMove(array, start_i, del_count, len, num_elements_to_add);
   } else {