Further updates for rails 7.2

[jpawlyn]

Description

Follow on from #2927 to make 2.x more compitable with Rails 7.2

Fixes # (issue)

Failure/Error: reflected_model = reflection.klass
     
     NoMethodError:
       undefined method `klass' for nil
     # /Users/jpawlyn/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/avo-2.52.0/app/controllers/avo/application_controller.rb:231:in `related_resource'
     # /Users/jpawlyn/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/avo-2.52.0/app/controllers/avo/application_controller.rb:126:in `set_related_resource'
     # /Users/jpawlyn/.rbenv/versions/3.3.4/lib/ruby/gems/3.3.0/gems/activesupport-7.2.1/lib/active_support/callbacks.rb:362:in `block in make_lambda'

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

Screenshots & recording

Manual review steps

1. Step 1
2. Step 2

Manual reviewer: please leave a comment with output from the test if that's the case.

[jpawlyn]

I can see there are 2 failing tests. Let me try debugging them

[jpawlyn]

I can't seem to get the tests to pass so closing for now