Using DiscoverableListener in Confluence Cloud Migration Assistant causes a NullPointerException during app assessment

Issue Summary

When using atlassian-app-cloud-migration-listener at the end of App Assessment and the app is set as Needed in Cloud, when the endpoint /rest/migration/latest/app/consent is called, a 500 error is thrown and this toast appears

Steps to Reproduce

1. Install an app that used atlassian-app-cloud-migration-listener
2. Go though App Assessment to the end

Expected Results

We get the expected display of the app.

Actual Results

The below exception is thrown in the atlassian-confluence.log file:

2021-09-30 13:33:54,312 ERROR [http-nio-1990-exec-4] [[Standalone].[localhost].[/confluence].[noop]] log Servlet.service() for servlet [noop] in context with 
path [/confluence] threw exception
org.codehaus.jackson.map.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.atlassian.migration.agent.dto.assessment.App
ListResponse["apps"]->java.util.ArrayList[1]->com.atlassian.migration.agent.dto.assessment.AppConsentDto["dataScopes"]->java.util.ArrayList[0])
...
Caused by: java.lang.NullPointerException

and the UI throws

Workaround

For now, developers can use https://developer.atlassian.com/platform/app-migration/testing/dev-mode/ to by pass App Assessment until this is resolved.