[php-src] PR #24512: Fix GH-24509: HTTP wrapper leaks Location buffer on empty Location header

Pull Request: https://github.com/php/php-src/pull/24512 Author: bercedev Fixes GH-24509 php_stream_http_response_headers_parse() used location_len == 0 to mean "no Location buffer allocated yet". An empty Location: header allocates a 1-byte buffer and leaves location_len at 0, so a later Location: header took the emalloc() branch again and leaked the first buffer. It now checks header_info->location == NULL. The struct is zeroed by php_stream_http_response_header_info_init(), and the pointer is set back to NULL wherever the buffer is handed off or freed. The new ext/standard/tests/http/gh24509.phpt sends Location: followed by Location: /abcdefghijklmno, then follows the redirect. On a debug build (--enable-debug --enable-pcntl --enable-posix) of PHP-8.4 without the fix it fails with: ``` ext/standard/http_fopen_wrapper.c(339) : Freeing 0x... (16 bytes), script=.../gh24509.php === Total 1 memory leaks detected === ``` With the fix it passes, and ext/standard/tests/http/ gives 71 passed, 14 skipped, 0 failed. I targeted PHP-8.4 because the same code is there.