Fix NRE and Disallow Missing Registration Page Leaves

[mukunku]

Bug

Fixes: https://github.com/NuGet/Home/issues/13377

Regression? Last working version: The NRE has been there since the code was written in #3462

Description

The original issue is just the wrong variable being used in the if check. However for some reason when doing dotnet tool restore in the dotnet 6 sdk the issue doesn't happen for us. But once we upgraded our project to use dotnet 8 the NRE started happening every time we ran dotnet tool restore. So this is sort of a "regression" for us because our in-house NuGet repo (cloudsmith) returns 404 if there are no active packages in a version range.

I think it makes sense to gracefully skip any missing leaf pages. We are already allowing 404's with the IgnoreNotFounds = true, flag. So I think not throwing an exception in a recoverable situation makes more sense here and it would help resolve our issue as well.

PR Checklist

• [x] PR has a meaningful title

• [x] PR has a linked issue.

• [x] Described changes

• Tests

  • [x] Automated tests added
  • OR
  • [ ] Test exception
  • OR
  • [ ] N/A

• Documentation

  • [ ] Documentation PR or issue filled
  • OR
  • [x] N/A

[mukunku]

@dotnet-policy-service agree company="StackOverflow"

[mukunku]

Seems like folks don't like my fix so going to close this out.