Apply libxml fix for undefined namespaces.

third_party/libxml/src/xpath.c

 /*
  * xpath.c: XML Path Language implementation
  *          XPath is a language for addressing parts of an XML document,
  *          designed to be used by both XSLT and XPointer
  *f
  * Reference: W3C Recommendation 16 November 1999
  *     http://www.w3.org/TR/1999/REC-xpath-19991116
  * Public reference:
  *     http://www.w3.org/TR/xpath
  *
@@ skipping 13333 matching lines @@
                     }
                     valuePush(ctxt, val);
                 } else {
                     const xmlChar *URI;
 
                     URI = xmlXPathNsLookup(ctxt->context, op->value5);
                     if (URI == NULL) {
                         xmlGenericError(xmlGenericErrorContext,
             "xmlXPathCompOpEval: variable %s bound to undefined prefix %s\n",
                                     (char *) op->value4, (char *)op->value5);
+                        ctxt->error = XPATH_UNDEF_PREFIX_ERROR;
                         return (total);
                     }
                     val = xmlXPathVariableLookupNS(ctxt->context,
                                                        op->value4, URI);
                     if (val == NULL) {
                         ctxt->error = XPATH_UNDEF_VARIABLE_ERROR;
                         return(0);
                     }
                     valuePush(ctxt, val);
                 }
@@ skipping 28 matching lines @@
                     if (op->value5 == NULL)
                         func =
                             xmlXPathFunctionLookup(ctxt->context,
                                                    op->value4);
                     else {
                         URI = xmlXPathNsLookup(ctxt->context, op->value5);
                         if (URI == NULL) {
                             xmlGenericError(xmlGenericErrorContext,
             "xmlXPathCompOpEval: function %s bound to undefined prefix %s\n",
                                     (char *)op->value4, (char *)op->value5);
+                            ctxt->error = XPATH_UNDEF_PREFIX_ERROR;
                             return (total);
                         }
                         func = xmlXPathFunctionLookupNS(ctxt->context,
                                                         op->value4, URI);
                     }
                     if (func == NULL) {
                         xmlGenericError(xmlGenericErrorContext,
                                 "xmlXPathCompOpEval: function %s not found\n",
                                         (char *)op->value4);
                         XP_ERROR0(XPATH_UNKNOWN_FUNC_ERROR);
@@ skipping 1734 matching lines @@
                          xmlXPathTranslateFunction);
 
     xmlXPathRegisterFuncNS(ctxt, (const xmlChar *)"escape-uri",
          (const xmlChar *)"http://www.w3.org/2002/08/xquery-functions",
                          xmlXPathEscapeUriFunction);
 }
 
 #endif /* LIBXML_XPATH_ENABLED */
 #define bottom_xpath
 #include "elfgcchack.h"