Description

isXMLDoc() throws an error if undefined given, starting from version 3.4.0

Test script:

jQuery.isXMLDoc(undefined)

jQuery 3.3.1 result:

false

jQuery 3.5.1 (currently the latest, but starting from 3.4.0) result:

Uncaught TypeError: Cannot read property 'namespaceURI' of undefined

Techinfo

Before the Sizzle update from 2.3.3 to 2.3.4 (see related commit below), isXML() function looked liked this:

isXML = Sizzle.isXML = function( elem ) {
	// documentElement is verified for cases where it doesn't yet exist
	// (such as loading iframes in IE - #4833)
	var documentElement = elem && (elem.ownerDocument || elem).documentElement;
	return documentElement ? documentElement.nodeName !== "HTML" : false;
};

This doesn't throw an error, when the elem is undefined, because it checks it.

In the update from 3.4.0, it looks like this:

isXML = Sizzle.isXML = function( elem ) {
	var namespace = elem.namespaceURI,
		docElem = ( elem.ownerDocument || elem ).documentElement;

	// Support: IE <=8
	// Assume HTML when documentElement doesn't yet exist, such as inside loading iframes
	// https://bugs.jquery.com/ticket/4833
	return !rhtml.test( namespace || docElem && docElem.nodeName || "HTML" );
};

This throws an error when the elem is undefined:
Uncaught TypeError: Cannot read property 'namespaceURI' of undefined

Please, if you can, bring back the previous functionality: undefined is not an XML node, so it should return a false boolean instead of a TypeError.

Thanks in advance!

Additional info

Related commit: d940bc0 (from line 562)
Related blog-post: https://blog.jquery.com/2019/04/10/jquery-3-4-0-released/