`$content-uri` value is empty in map mode

{
    "message": "Required cardinality of value in 'xsl:variable name=\"Q{}content-uri\"' expression is exactly one; supplied value is empty",
    "stack": "Error\n    at new I (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:179:51)\n    at B (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:762:327)\n    at https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:763:120\n    at https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:813:115\n    at https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:763:29\n    at https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:520:321\n    at Object.push (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:523:400)\n    at g.bf (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:1132:330)\n    at https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:1130:192\n    at ca.forEachItem (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:306:389)\n    at g.Lb (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:1130:159)\n    at HTMLDocument.Y (https://linkeddatahub.com/static/com/atomgraph/linkeddatahub/js/saxon-js/SaxonJS2.rt.js:1160:31)",
    "name": "XError",
    "code": "XTTE0570",
    "xsltLineNr": "423",
    "xsltModule": "map.xsl"
}

Observed on https://linkeddatahub.com/demo/northwind-traders/employees/2/?mode=https%3A%2F%2Fw3id.org%2Fatomgraph%2Fclient%23MapMode

AtomGraph / LinkedDataHub

`$content-uri` value is empty in map mode #152