Fix bogus deopt in BuildEmitDeepCopy for holey arrays.

R=verwaest@chromium.org
BUG=chromium:242924
TEST=mjsunit/regress/regress-crbug-242924

Review URL: https://codereview.chromium.org/15735012

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14757 ce2b1a6d-e550-0410-aec6-3dcde31c8c00