DOMDocument::loadXML throws ValueError for empty string since PHP 8

[TimWolla]

… and this is not yet documented, neither as a fact in the errors section, nor as a changelog entry.

see:

doc-en/reference/dom/domdocument/loadxml.xml

Lines 55 to 59 in 7c9f1ad

	<para>
	If an empty string is passed as the <parameter>source</parameter>,
	a warning will be generated. This warning is not generated by libxml
	and cannot be handled using libxml's error handling functions.
	</para>

and

https://3v4l.org/qEWjm

[cmb69]

Yeah, most ValueErrors are not documented yet. #163 is still work in progress,