Update the code so that calculations can still be run even if a refer…

[ughstudios]

Full description in #24 24

Checklist

• [ ] Keep pull requests small so they can be easily reviewed.
• [ ] Update the documentation, please follow the numpy style guide.
• [ ] Update tests.
• [ ] Categorize the PR by setting a good title and adding one of the labels: bug, feature, ui, change, documentation, breaking, ci as they show up in the changelog.
• [ ] Link this PR to related issues by using closing keywords.
• [ ] Add a milestone to the PR for the intended release.
• [ ] Request a review from another developer.

[cmutel]

This will fix things for now, but the broader problem (https://github.com/LCA-ActivityBrowser/activity-browser/issues/1301) still remains.