allow null values for forge update mutation

[ctmckenna]

Description of the change

default forge config has null values on finishPage. To
edit forge config without changing finishPage, we need to allow
those null values

Currently if any value is null graphQLUploadSchemaIsValid fails on line 20 when it tries to dereference schema to check if schema.constructor.name === 'Object'

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Fixes #1

Checklists

Development

• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development
• No previous tests unrelated to the changed code fail in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached.
• At least one reviewer has been requested
• Changes have been reviewed by at least one other engineer
• The relevant project board has been selected in Projects to auto-link to this pull request

[newhouse]

Awesome, thanks!

[newhouse]

This has been published in 2.7.2