Overlay layers are not rendered in the static image

[mprins]

expected behaviour

When an overlay layer:

• agslayer
• osmlayer
• wmslayer
• wmtslayer
• ...

is specified and default visibility is true it should be rendered in the static image

actual behaviour

Overlay layers are not rendered.

steps to reproduce actual behaviour

Add a map to a page and add an overlay, eg.

<olmap id="olmap" width="750px" height="650px" lat="50.2" lon="5.4" zoom="9" statusbar="1" toolbar="1" controls="1" poihoverstyle="0" baselyr="terrain" gpxfile="" kmlfile="beschrijvingen:belgie:sitemap.kml" geojsonfile="" summary="Kaart met in- en uitstap punten, beschrijvingen en vandaag bevaarbare trajecten">

</olmap>

<olmap_agslayer id="olmap" name="vandaag te bevaren" url="https://geoservices2.wallonie.be/arcgis/rest/services/APP_KAYAK/KAYAK/MapServer" attribution="kayak.environnement.wallonie.be" visible="true" layers="show:0,1,2,3,4,7"></olmap_agslayer>