Checks for empty array case added before casting elements to FixedDoubleArray.

BUG=chromium:369450
LOG=N
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/264973008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21118 ce2b1a6d-e550-0410-aec6-3dcde31c8c00