Fix "Cannot read property '__error' of null" error

[chrisbreiding]

• Closes Cannot read property '__error' of null #7518

User facing changelog

• Fixed a regression in 4.6.0 where an XHR response without a body would cause the error Cannot read property '__error' of null

Additional Details

• This was introduced from an error during decaffeination in Decaff driver part 4 #7227

PR Tasks

• Have tests been added/updated?
• Has the original issue been tagged with a release in ZenHub?
• N/A Has a PR for user-facing changes been opened in cypress-documentation?
• N/A Have API changes been updated in the type definitions?
• N/A Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

Thanks for the contribution! Below are some guidelines Cypress uses when doing PR reviews.

• Please write [WIP] in the title of your Pull Request if your PR is not ready for review - someone will review your PR as soon as the [WIP] is removed.
• Please familiarize yourself with the PR Review Checklist and feel free to make updates on your PR based on these guidelines.

PR Review Checklist

If any of the following requirements can't be met, leave a comment in the review selecting 'Request changes', otherwise 'Approve'.

User Experience

• The feature/bugfix is self-documenting from within the product.
• The change provides the end user with a way to fix their problem (no dead ends).

Functionality

• The code works and performs its intended function with the correct logic.
• Performance has been factored in (for example, the code cleans up after itself to not cause memory leaks).
• The code guards against edge cases and invalid input and has tests to cover it.

Maintainability

• The code is readable (too many nested 'if's are a bad sign).
• Names used for variables, methods, etc, clearly describe their function.
• The code is easy to understood and there are relevant comments explaining.
• New algorithms are documented in the code with link(s) to external docs (flowcharts, w3c, chrome, firefox).
• There are comments containing link(s) to the addressed issue (in tests and code).

Quality

• The change does not reimplement code.
• There's not a module from the ecosystem that should be used instead.
• There is no redundant or duplicate code.
• There are no irrelevant comments left in the code.
• Tests are testing the code’s intended functionality in the best way possible.

Internal

• The original issue has been tagged with a release in ZenHub.

[cypress]

---

Test summary

7707 • 0 • 112 • 0

---

Run details

Project	cypress
Status	Passed
Commit	f0780fd
Started	May 29, 2020 2:22 PM
Ended	May 29, 2020 2:29 PM
Duration	07:16 💡
OS	Linux Debian - 10.1
Browser	Multiple

View run in Cypress Dashboard ➡️

---

This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard

[jennifer-shehane]

I manually confirmed this fixes the issue. Tests look great. 👍

[colemars]

Just encountered this - awesome to see it's already been traced and handled.

Thanks @jennifer-shehane and everyone