Content selector All_Maven2 is in use and cannot be deleted error appears if migrate nuget from Nexus Repository 2 to 3

The current issue is reproducible for now only in the feature branch until merge to master.
Check status of the ticket: https://issues.sonatype.org/browse/NEXUS-26490

Steps to reproduce: 

1. Prepare nexus 2 for migration
   1. Create nuget-hosted repository
   2. Add some nupkg package to the repository. chek in the attachment.
   3. Add upgrade capabilities
2. Get nexus source from branch NEXUS-26490_nuget_nexus2-3_migration
3. Start nexus3
4. Add Upgrade Capabilities
5. Start Upgrade process 
   1. Specifu nexus2 url and token
   2. On next page check  checkboxes: Repository configuration and content,
       
      Server configuration
   3. On the next page leave everything as is.
   4. On next page select nuget-repository for migration
   5. On next page click Begin button. 

Actual:

Expected: no errors