[runtime] Don't try to create empty enum cache.

When copying maps and the new map has no enumerable properties we
should not try to initialize an enum cache.

This happens if the deprecation is due to making the only property in
a map non enumerable.

Bug: chromium:1472317, chromium:1470668
Change-Id: I7a6af63e50dc30592e2caacce0caccfb31f534cf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4775581
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Olivier Fl├╝ckiger <olivf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#89534}
diff --git a/src/objects/map-updater.cc b/src/objects/map-updater.cc
index 7a864d9..9c20491 100644
--- a/src/objects/map-updater.cc
+++ b/src/objects/map-updater.cc
@@ -1040,7 +1040,8 @@
   split_map->ReplaceDescriptors(isolate_, *new_descriptors);
 
   // If the old descriptors had an enum cache, make sure the new ones do too.
-  if (old_descriptors_->enum_cache()->keys()->length() > 0) {
+  if (old_descriptors_->enum_cache()->keys()->length() > 0 &&
+      new_map->NumberOfEnumerableProperties() > 0) {
     FastKeyAccumulator::InitializeFastPropertyEnumCache(
         isolate_, new_map, new_map->NumberOfEnumerableProperties());
   }