Array.prototype.slice should only normalize result 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 633a8a255ffdd2bdb2a1d69db92206fe11417a3e..671e507a1568bed82f41a6b1f7040c6493e6c867 100644
--- a/src/js/array.js
+++ b/src/js/array.js
@@ -659,7 +659,7 @@ function ArraySlice(start, end) {
 
   if (UseSparseVariant(array, len, IS_ARRAY(array), end_i - start_i)) {
     %NormalizeElements(array);
-    %NormalizeElements(result);
+    if (IS_ARRAY(result)) %NormalizeElements(result);
     SparseSlice(array, start_i, end_i - start_i, len, result);
   } else {
     SimpleSlice(array, start_i, end_i - start_i, len, result);