[php-src] PR #23467: Fix out-of-bounds read on empty Location header in HTTP wrapper

Pull Request: https://github.com/php/php-src/pull/23467 Author: iliaal When a server sends a redirect with an empty Location header, the wrapper allocates a single byte for it and the relative-redirect branch then reads location[1], one byte past the allocation, so a hostile server can make the over-read pick up heap garbage and turn the redirect target into the current path plus junk instead of the host root. The second-byte dereference is now guarded by header_info.location_len; an empty Location deterministically redirects to the host root. Sibling audit found no other unguarded indexing of header_info.location.