wrong order of mixed terms with ORDER BY

[pchampin]

According to the spec about ORDER BY:

SPARQL also fixes an order between some kinds of RDF terms that would not otherwise be ordered:

• (Lowest) no value assigned to the variable or expression in this solution.
• Blank nodes
• IRIs
• RDF literals

So the following query:

SELECT ?x { VALUES ?x { 3 <x:1> 4 <x:2> } } ORDER BY ?x

should produce the result in the following order: <x:1> <x:2> 3 4.

But currently, Qlever produces them in that order: 3 4 <x:1> <x:2>

See https://qlever.dev/wikidata/liLuRo