Dont crash on worker threads that have no PID, when reporting on stopped workers.

[underdarknl]

We are seeing errors, and subsequent restart loops for missing workers. Instead of recreating the missing workers, we crash on the missing PID when trying to emit a warning.

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[dekkers]

PR can't be merged because it doesn't pass pre-commit. It is recommended to install the pre-commit hook in your git repositroy so this doesn't happen again with future PRs, see the developer documentation at https://docs.openkat.nl/developer-documentation/contributor/guidelines/development.html#pre-commit.

We also made changes to the CLA bot which unfortunately means that it doesn't remember who signed the CLA in the past, so you need sign it again.