Fix TypeError with .fit files

[rpellerin]

Context

Fixes the following error when using a .fit file.

Contributor Checklist

• [x] Review Contribution Guidelines
• [x] Agree to the terms of Developer Certificate of Origin.
• [x] Make sure all contributed code can be distributed under the terms of the MIT Licence
• [x] Check "Allow edit from maintainers" option in pull request so that additional changes can be pushed by maintainers if required.
• [ ] Unit tests created/updated (under tests) to verify logic, and approval tests for UI Widgets
• [ ] Update Examples - Under build-scripts/examples, and regenerate examples docs if required ( make doc-examples )
• [ ] Ensure that tests pass locally - this can be tricky for approval tests with maps or text though.
• [ ] Check that pre-release tests work ( make test-distribution )

[time4tea]

Thanks for this contribution. I didnt realise that there was a problem when using a fit file that contains "gps_accuracy" tags. I think that is probably the problem. I'll see if i can make a test case to show the issue.

[time4tea]

Yes this definitely doesn't work! - Your fix does fix the problem - thank you! - I won't merge this PR, but I've taken your commits into main. Thanks for the contribution.