[libxml2] Fix memory leaks in xmlXPathParseNameComplex error paths

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 93a1d2238087c3acc650ba741067f34fb94905fc
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Tue Apr 16 13:37:47 2019 +0200

    Fix memory leaks in xmlXPathParseNameComplex error paths
    
    Found by OSS-Fuzz.

 xpath.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)
---
diff --git a/xpath.c b/xpath.c
index a3a2aa62..1c567d78 100644
--- a/xpath.c
+++ b/xpath.c
@@ -10004,15 +10004,19 @@ xmlXPathParseNameComplex(xmlXPathParserContextPtr ctxt, int qualified) {
                   (IS_COMBINING(c)) ||
                   (IS_EXTENDER(c))) {
                if (len + 10 > max) {
+                    xmlChar *tmp;
                     if (max > XML_MAX_NAME_LENGTH) {
+                        xmlFree(buffer);
                         XP_ERRORNULL(XPATH_EXPR_ERROR);
                     }
                    max *= 2;
-                   buffer = (xmlChar *) xmlRealloc(buffer,
-                                                   max * sizeof(xmlChar));
-                   if (buffer == NULL) {
+                   tmp = (xmlChar *) xmlRealloc(buffer,
+                                                max * sizeof(xmlChar));
+                   if (tmp == NULL) {
+                        xmlFree(buffer);
                        XP_ERRORNULL(XPATH_MEMORY_ERROR);
                    }
+                    buffer = tmp;
                }
                COPY_BUF(l,buffer,len,c);
                NEXTL(l);