Fix CTC matching for emtpy frames

[bentaculum]

Proposed Change

Fixes #138.

Types of Changes

What types of changes does your code introduce? Put an x in the boxes that apply.

• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature or enhancement
• [ ] Documentation update
• [ ] Tests and benchmarks
• [ ] Maintenance (e.g. dependencies, CI, releases, etc.)

Which topics does your change affect? Put an x in the boxes that apply.

• [ ] Loaders
• [x] Matchers
• [ ] Track Errors
• [ ] Metrics
• [x] Core functionality (e.g. TrackingGraph, run_metrics, cli, etc.)

Checklist

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• [x] I have read the developer/contributing docs.
• [ ] I have added tests that prove that my feature works in various situations or tests the bugfix (if appropriate).
• [ ] I have checked that I maintained or improved code coverage.
• [x] I have checked the benchmarking action to verify that my changes did not adversely affect performance.
• [ ] I have written docstrings and checked that they render correctly in the Read The Docs build (created after the PR is opened).
• [ ] I have updated the general documentation including Metric descriptions and example notebooks if necessary.

[bentaculum]

Just noticed, the tests for the CTCMatcher are a bit minimalistic in general, it wouldn't hurt to add a test for the CTCMatcher that uses a non-equal GT and prediction.

[cmalinmayor]

@DragaDoncila @bentaculum I added the suggested tests. I also removed the unusued TrackingGraph.get_nodes_in_frame() function in favor of the implemented defaultdict approach. I believe the failing tests are due to the pandas dependency issue and not the actual tests (since they run locally) but I will have to fix that and merge to be sure.

[bentaculum]

Awesome, thanks :)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (f4398e8) 91.64% compared to head (96a57cd) 91.63%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #139 +/- ## ========================================== - Coverage 91.64% 91.63% -0.02% ========================================== Files 19 19 Lines 826 825 -1 ========================================== - Hits 757 756 -1 Misses 69 69 ```

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