Fix regress-851.js to use assertNull instead of assertFalse.

Review URL: http://codereview.chromium.org/3232002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5365 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/regress/regress-851.js

@@ -28,5 +28,5 @@
 var i = 0;
 for (var i = 0; i < 10000; i++) {
   Object.freeze({});
-  assertFalse(JSON.stringify({x: null}).match(/\0/));
+  assertNull(JSON.stringify({x: null}).match(/\0/));
 }