[libxml2] Unlink node before freeing it in xmlSAX2StartElement

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 0ed6addb8f165ae533fbe812e4a973c7b682ec7e
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sat Sep 22 15:41:01 2018 +0200

    Unlink node before freeing it in xmlSAX2StartElement
    
    The node may have been added to the document already, so it must be
    unlinked first. Thanks to David Kilzer for spotting this.

 SAX2.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/SAX2.c b/SAX2.c
index 49ce566c..ac3ab19a 100644
--- a/SAX2.c
+++ b/SAX2.c
@@ -1666,6 +1666,7 @@ xmlSAX2StartElement(void *ctx, const xmlChar *fullname, const xmlChar **atts)
     xmlGenericError(xmlGenericErrorContext, "pushing(%s)\n", name);
 #endif
     if (nodePush(ctxt, ret) < 0) {
+        xmlUnlinkNode(ret);
         xmlFreeNode(ret);
         return;
     }
@@ -2340,6 +2341,7 @@ xmlSAX2StartElementNs(void *ctx,
      * We are parsing a new node.
      */
     if (nodePush(ctxt, ret) < 0) {
+        xmlUnlinkNode(ret);
         xmlFreeNode(ret);
         return;
     }