🥅 Raise an error instead of returning `None` where a dict is expected

Fixes

Fixes https://github.com/FCP-INDI/C-PAC/pull/2059#discussion_r1472295222 by @shnizzedy with https://github.com/FCP-INDI/C-PAC/pull/2059#discussion_r1483106483 by @nx10

Description

https://github.com/FCP-INDI/C-PAC/blob/85737a19957a212586de173fb18d5ffe0ad6ed40/CPAC/nuisance/utils/utils.py#L639-L640 It hasn't seemed to cause a problem, but I don't understand why this case would return None instead of pipeline_resource_pool or {}

If no one knows you could turn it into an error? Maybe it just never happens?

This just changes that return None into a raise LookupError

Checklist

[x] My pull request has a descriptive title (not a vague title like Update index.md).
[x] My pull request targets the intial-run/ruff branch of the repository.
[x] My commit messages follow best practices.
[x] My code follows the established code style of the repository.
[ ] I added tests for the changes I made (if applicable).
[ ] I updated the changelog.
[ ] I added or updated documentation (if applicable).
[ ] I tried running the project locally and verified that there are no visible errors.

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FCP-INDI / C-PAC