REST API - Layer Group creation does not work when using default styles

[AlexGacon]

If I want to create a layer group with the REST API with default styles for some of the layers, I have a 500 error code on GeoServer Cloud 1.9.1 which cannot be reproduced in GeoServer 2.26.1.

The creation through the web UI is working correctly.

Example of REST payload:

<layerGroup>
  <name>test_api</name>
  <mode>SINGLE</mode>
  <title>test_api</title>
  <workspace>
    <name>nexsis</name>
  </workspace>
  <publishables>
    <published type="layerGroup">
      <name>nexsis:ligne_electrique_pylone</name>
      </published>
      <published type="layerGroup">
        <name>nexsis:limites_administratives</name>
        </published>
      </publishables>
      <styles>
        <style/>
        <style/>
      </styles>
      <bounds>
        <minx>-180.0</minx>
        <maxx>180.0</maxx>
        <miny>-90.0</miny>
        <maxy>90.0</maxy>
        <crs>EPSG:4326</crs>
      </bounds>
    </layerGroup>