Error on index search

When searching for "Berlin" in the index (having selected the "Personen und Werke" as well as the "Geographisches Register" filter) I get the following error:

<exception>
<path>/db/apps/SADE/modules/view.xql</path>
<message>
err:XPTY0004 Cardinality error in switch operand [at line 228, column 9, source: /db/apps/SADE/modules/fontane/index-api.xqm] In function: index:rendered-entity(xs:string) [198:5:/db/apps/SADE/modules/fontane/index-api.xqm] ixv:item(item()*, item()*, xs:string?, xs:string?) [-1:-1:/db/apps/SADE/modules/fontane/index-viewer.xqm] templates:process-output(element(), map(*), item()*, element()) [211:9:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:call-by-introspection(element(), map(*), map(*), function(*)) [189:28:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:call(item(), element(), map(*)) [137:36:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [148:81:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [148:81:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [148:81:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [148:81:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [148:81:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [428:17:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process-output(element(), map(*), item()*) [230:9:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process-output(element(), map(*), item()*, element()) [211:9:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:call-by-introspection(element(), map(*), map(*), function(*)) [189:28:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:call(item(), element(), map(*)) [137:36:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [133:51:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:process(node()*, map(*)) [90:9:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql] templates:apply(node()+, function(*), map(*)?, map(*)?) [65:5:/opt/sade/etc/../data/expathrepo/shared-0.8.5/content/templates.xql]
</message>
</exception>

Sample URL: https://fontane-nb.dariah.eu/register.html?e=Stadtschloss_Berlin

On the other hand it works fine for https://fontane-nb.dariah.eu/register.html?e=Kunerts-Kamp_Schauplatz.