Fix CurrentMapForDeprecated() to return MaybeHandle instead of a null handle.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index ed3a8b6ee34eb72a14975eb6dc6e22d5099ad39f..97b6a60b3f5656d1a73a721866841b90c42f08d1 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -281,8 +281,7 @@ class SmallMapList V8_FINAL {
   int length() const { return list_.length(); }
 
   void AddMapIfMissing(Handle<Map> map, Zone* zone) {
-    map = Map::CurrentMapForDeprecated(map);
-    if (map.is_null()) return;
+    if (!Map::CurrentMapForDeprecated(map).ToHandle(&map)) return;
     for (int i = 0; i < length(); ++i) {
       if (at(i).is_identical_to(map)) return;
     }