Fix error handler in graphql client

[5n00p4eg]

WHY are these changes introduced?

In some cases, fetch response is not available for error handling, so type error appears:

TypeError: Cannot read properties of undefined (reading 'headers')

Related issues: Shopify/shopify-app-js#764

WHAT is this pull request doing?

In case of response object is not avaliabe GraphqlQueryError is raised directly with outer response data.

Type of change

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

Checklist

• I have used yarn changeset to create a draft changelog entry (do NOT update the CHANGELOG.md file manually)
• I have added/updated tests for this change
• I have documented new APIs/updated the documentation for modified APIs (for public APIs)

[paulomarg]

Thank you so much for contributing, we appreciate it! I think this is the right idea, but I have some thoughts:

1. There are a few other places that use this same logic, we should probably not assume we get a response in all of them. I think it would be better to have this code inside of throwFailedRequest. We could make response accept Response | undefined and then throw first thing if no response is present. That way all of these cases would behave the same way.
2. We should have a test for this case, at least for the admin and storefront clients - you can use queueError instead of queueMockResponse in the test file to trigger this scenario

[5n00p4eg]

@paulomarg Take a look, please

[paulomarg]

Looks great, thank you!