Don't cleanup doc reference of unlinked node.

ZigzagAK · web-flow · commit 7a7bc8e70d7d · 2023-12-14T13:27:20.000+03:00
This is cause if incorrect free in xmlFreeNode (DICT_FREE(cur-&gt;name)).
diff --git a/xmlua/libxml2.lua b/xmlua/libxml2.lua
@@ -572,7 +572,6 @@ end
 
 function libxml2.xmlUnlinkNode(node)
   xml2.xmlUnlinkNode(node)
-  xml2.xmlSetTreeDoc(node, ffi.NULL)
   return ffi.gc(node, xml2.xmlFreeNode)
 end
 
