Error: release-please failed: Cannot read properties of undefined (reading 'replace')

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#### Environment details

- Programming language: monorepo - TS, Python, Go, Kotlin, CSharp, Swift
- OS: Ubuntu latest
- Language runtime version:
- Package version: v4 tested with v4 and with v4.1.2 specifically

#### Steps to reproduce

1. Run release-please-action in the [sdk-codegen repo](https://github.com/looker-open-source/sdk-codegen).
2. Expect to update the existing PR, instead get `Error: release-please failed: Cannot read properties of undefined (reading 'replace')`.

Making sure to follow these steps will guarantee the quickest resolution possible.

Thanks!

Start by reproducing the release-please-action failure in the linked sdk-codegen repository, using the reported v4 and v4.1.2 versions and Ubuntu latest. Trace the action's release flow around the existing pull request; done means the action updates that PR without the reported undefined replace error.

Written by the indexing model from the issue text.