libxml2: fix CVE-2025-49795

libxml2: fix CVE-2025-49795

A NULL pointer dereference vulnerability was found in libxml2 when
processing XPath XML expressions. This flaw allows an attacker to
craft a malicious XML input to libxml2, leading to a denial of service.

Pick commit from 2.13 branch

Reference:
https://security-tracker.debian.org/tracker/CVE-2025-49795

Upstream-patch:
https://gitlab.gnome.org/GNOME/libxml2/-/commit/62048278a4c5fdf14d287dfb400005c0a0caa69f

Signed-off-by: Divya Chellam <divya.chellam@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>