[libxml2/2.9] Fix leak of xmlElementContent

[Nick Wellnhofer <nwellnhof src gnome org>]

commit d2f48e211567454177e8a288782c3598d33995eb
Author: David Kilzer <ddkilzer apple com>
Date:   Wed Apr 6 18:05:20 2022 -0700

    Fix leak of xmlElementContent
    
    * valid.c:
    (xmlCopyDocElementContent):
    - Set `tmp->parent` properly to fix a leak that occurs in
      xmlFreeDocElementContent().
    - Appears to be a regresion from cee2b3a5f1.
    
    Found by OSS-Fuzz Issue 44509.

 valid.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/valid.c b/valid.c
index 9684683a..ed3c8503 100644
--- a/valid.c
+++ b/valid.c
@@ -1052,6 +1052,7 @@ xmlCopyDocElementContent(xmlDocPtr doc, xmlElementContentPtr cur) {
            tmp->type = cur->type;
            tmp->ocur = cur->ocur;
            prev->c2 = tmp;
+           tmp->parent = prev;
            if (cur->name != NULL) {
                if (dict)
                    tmp->name = xmlDictLookup(dict, cur->name, -1);