[runtime] Don't crash when creating an instance of a class inherited from a Proxy.

test/mjsunit/regress/regress-v8-4972.js

Index: test/mjsunit/regress/regress-v8-4972.js
diff --git a/test/message/regress/regress-4829-1.js b/test/mjsunit/regress/regress-v8-4972.js
similarity index 79%
copy from test/message/regress/regress-4829-1.js
copy to test/mjsunit/regress/regress-v8-4972.js
index 1ad5feda8cb96cd24e4c47f7407c9699d150c327..689ae039ba3b0e38d4796b0deca5b5eb23c4cbfd 100644
--- a/test/message/regress/regress-4829-1.js
+++ b/test/mjsunit/regress/regress-v8-4972.js
@@ -2,6 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-function tag() {}
-
-tag(tag`\xyy`);
+new class extends new Proxy(class {},{}) {}