add test for nested allOf + $ref

[shockey]

originally from @ponelat in #1264

Description

This adds a test, highlighting a bug.
With nested allOfs + $refs.

Example defintition fragment:

definitions:
  Alpha:
    allOf:
    - type: object
    properties:
      test:
        $ref: '#/definitions/Bravo'
 
  Bravo:
    allOf: 
      - type: object
        properties:
          two: 
            type: string

Causes: TypeError: Cannot read property 'Alpha' of undefined

Types of changes

• No code changes (changes to documentation, CI, metadata, etc)
• Dependency changes (any modification to dependencies in package.json)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[shockey]

Okay, everything appears good now - looks like allOf was dying on a replace patch, which may have been selected for the allOf plugin's consideration incorrectly due to the nested structure we have.

I simply sidestepped this by not trying to keep looking for a value that doesn't exist. The tests pass, @ponelat I'm going to tag you for review to ensure this is the spirit of what you were looking for here.

[shockey]

Merging, per @ponelat:

I'm happy with it being Just Merged. It may not be the solution, but again, its a harmless looking PR... what could go wrong?

he said, on the eve of Friday night... the 13th!

[ponelat]

Thanks @shockey this fixes my issue!