Fix xmlGetNodePath with invalid node types

Make xmlGetNodePath return NULL instead of invalid XPath when hitting
unsupported node types like DTD content.

Reported here:
https://mail.gnome.org/archives/xml/2021-January/msg00012.html

Original report:
https://bugs.php.net/bug.php?id=80680

1 files changed, 3 insertions, 1 deletions

diff --git a/tree.c b/tree.c
index dbc87aa7..c707f598 100644
--- a/tree.c
+++ b/tree.c
@@ -4893,7 +4893,9 @@ xmlGetNodePath(const xmlNode *node)
             }
             next = ((xmlAttrPtr) cur)->parent;
         } else {
-            next = cur->parent;
+            xmlFree(buf);
+            xmlFree(buffer);
+            return (NULL);
         }
 
         /*