[Bug] eXist-db failing to match the error in the query and throwing different error

[marmoure]

eXide is showing the wrong error when trying to evaluate this query:

xquery version "3.1";

declare function local:parent-collection($collection-path as xs:string) as xs:string? {
   let $parent-collection-path := replace($collection-path, "(/.+)/.*", "$1")
   return
       if ($parent-collection-path eq $collection-path or not(starts-with($parent-collection-path, "/db")))
       then
           ()
       else
           $parent-collection-path
};

declare %private function local:ascend($collection-path as xs:string, $group-name as xs:string, $collection-permission as xs:string) as empty-sequence() {
    if (not(starts-with($collection-path, "/db")))
    then
       ()
    else
       let $_ := sm:add-group-ace(xs:anyURI($collection-path), $group-name, true(), $collection-permission)
       return
            local:ascend(local:parent-collection($collection-path), $group-name, $collection-permission)
};

local:ascend("/db/apps/test-app/test-dir","monex","r-x")

exerr:ERROR The actual return type does not match the sequence type declared in the function's signature: local:ascend(xs:string, xs:string, xs:string) empty-sequence(). Expected cardinality: empty, got 0. [at line 13, column 39, source: String/6893983447689836372]
In function:
	local:ascend(xs:string, xs:string, xs:string) [23:1:String/6893983447689836372]

The issue is saying that the return type of local:ascend is wrong, whilst this has nothing to do with the issue at hand
also it is saying: Expected cardinality: empty, got 0. which should be the same!
The first parameter of local:ascend is expecting xs:string whilst local:parent-collection returns xs:string?.
If I change the first parameter of local:ascend from type xs:string to type xs:string?, then the error goes away.
The fix is not related to the error that is shown, therefore I conclude that eXide/eXist-db is showing the wrong error for the actual problem.

• eXist 7.0.0-SNAPSHOT 92b8b9d
• Java 17
• OS Windows 10