CLSA-2026-1777878328 libxml2: Fix of 2 CVEs

CVE-2018-14404: fix NULL pointer dereference in xmlXPathCompOpEval when parsing an invalid XPath expression in the XPATHOPAND or XPATHOPOR case - CVE-2019-19956: fix memory leak in xmlParseBalancedChunkMemoryRecover related to newDoc-oldNs...