bug of RapidXML when the value of a xml node is null

Question

If the value of node in the xml is null, when we print the xml node, the node has no start tag, but only the end tag. For example:

xml_document<char> doc;
doc.append_node(doc.allocate_node(rapidxml::node_element, "mynode", ""));
ofstream ofs("test.xml");
ofs<<doc;

the content of test.xml is:

</mynode>

the expected content of test.xml is

<mynode></mynode>

Is this a bug of rapidxml