CVE-2025-71450: inih before r63 Stack Buffer Under-Read in ini_parse_stream Discard Loop

inih before r63 contains a one-byte stack buffer under-read in iniparsestream() in ini.c that allows attackers to read abyss[-1] via an embedded NUL byte after an overlong line. Attackers can supply an INI file or string with a line of at least INIMAXLINE-1 bytes followed by a NUL byte, causing undefined behavior reported by memory sanitizers.