Internal HandleScope::CloseAndEscape crashes on NULL handles.

R=kmillikin@chromium.org
BUG=v8:1529
TEST=mjsunit/regress/regress-1529

Review URL: http://codereview.chromium.org/7309004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8527 ce2b1a6d-e550-0410-aec6-3dcde31c8c00