Avoid indexing into a string when it's empty to avoid an assertion failure when using _GLIBCXX_DEBUG.
Avoid indexing into a string when it's empty to avoid an assertion failure
when using _GLIBCXX_DEBUG.

Patch by tzik@chromium.org
Original review http://codereview.chromium.org/7198018/


datacratic/DasDB,datacratic/DasDB,datacratic/DasDB,datacratic/DasDB,datacratic/DasDB