PUT collection REST API returns 500 when rights check method configuration is omitted from request body

Summary

Sending a PUT request to update a collection that has a rights_check_method configured, without including rights_check_method_configuration in the request body, results in a 500 Internal Server Error. The update is completely rejected, even for unrelated fields.

Steps to reproduce

1. Ensure a collection with a rights check method exists. In the following, it assumed that a collection "Sandbox" exists and the standard demo Admin user exists.
2. Send a partial PUT updating only the title:

   curl -u Admin:admin -X PUT -H "Content-Type: application/json" \
   -d '{"title": "Sandbox"}' \
   http://localhost:8080/xwiki/rest/wikis/xwiki/aiLLM/collections/Sandbox
   

Expected result:

HTTP 200 with the updated collection object; only the title field is changed, all other properties (including rights_check_method) remain unchanged.

Actual result:

HTTP 500 Internal Server Error. Server log shows:

ERROR .i.r.DefaultCollectionResource - Error updating collection [Sandbox].  
org.xwiki.contrib.llm.IndexException: Authorization configuration object is not of the correct type [class java.lang.Object]
        at org.xwiki.contrib.llm.internal.DefaultCollection.setAuthorizationConfiguration(DefaultCollection.java:338)
        at org.xwiki.contrib.llm.rest.JSONCollection.applyTo(JSONCollection.java:115)
        at org.xwiki.contrib.llm.internal.rest.DefaultCollectionResource.putCollection(DefaultCollectionResource.java:94