We early return here
92a4311868/Library/Homebrew/utils/github/api.rb (L220)
, but don't then handle that through the stack.
Repro:
```console
❯ HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_GITHUB_API=1 brew bump-formula-pr --write-only --version 1.2.3 --no-audit jq
Error: undefined method `[]' for nil:NilClass
Do not report this issue until you've run `brew update` and tried again.
Warning: Removed Sorbet lines from backtrace!
/opt/homebrew/Library/Homebrew/utils/github.rb:565:in `block in fetch_pull_requests'
/opt/homebrew/Library/Homebrew/utils/github/api.rb:334:in `paginate_graphql'
/opt/homebrew/Library/Homebrew/utils/github.rb:564:in `fetch_pull_requests'
/opt/homebrew/Library/Homebrew/utils/github.rb:628:in `check_for_duplicate_pull_requests'
/opt/homebrew/Library/Homebrew/dev-cmd/bump-formula-pr.rb:456:in `check_open_pull_requests'
/opt/homebrew/Library/Homebrew/dev-cmd/bump-formula-pr.rb:135:in `run'
/opt/homebrew/Library/Homebrew/brew.rb:89:in `<main>'
Rerun with `--verbose` to see the original backtrace
```
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