USN-8526-2: libheif vulnerabilities

USN-8526-1 fixed vulnerabilities in libheif. This update provides the corresponding updates for CVE-2026-47709 and CVE-2026-47714 in Ubuntu 24.04 LTS. Original advisory details: Junyi Liu discovered that libheif had a null pointer dereference in its image tiling interface. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-47709) Calvin Young and Enoch Chow discovered that libheif had an integer overflow in its inline mask size calculation. An attacker could possibly use this issue to cause a denial of service or obtain sensitive information. (CVE-2026-47714)