[libxml2] Don't try to copy children of entity references

[Nick Wellnhofer <nwellnhof src gnome org>]

commit d314046f897fbb0e3141108012b668374e665020
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sat Apr 23 17:41:44 2022 +0200

    Don't try to copy children of entity references
    
    This would result in an error, aborting the whole copy operation.
    Regressed in commit 7618a3b1.
    
    Fixes #371.

 tree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/tree.c b/tree.c
index 07499484..2b02df3d 100644
--- a/tree.c
+++ b/tree.c
@@ -4372,7 +4372,8 @@ xmlStaticCopyNode(xmlNodePtr node, xmlDocPtr doc, xmlNodePtr parent,
                 insert->last = copy;
             }
 
-            if (cur->children != NULL) {
+            if ((cur->type != XML_ENTITY_REF_NODE) &&
+                (cur->children != NULL)) {
                 cur = cur->children;
                 insert = copy;
                 continue;