tests: Complete the test suite for `TriesOverview` Component

[EshaanAgg]

Summary

• Completed the test suite for the TriesOverview Component with VTL
• I refactored some of the logic of the component as well, as I felt that the same better described the intended functionality of the component rather than passing or checking for null values. I might be misunderstanding some functionality or missing out on some edge cases, so a second set of eyes would be helpful!

References

Parent Issue

Testing checklist

• [X] Contributor has fully tested the PR manually
• [X] If there are any front-end changes, before/after screenshots are included
• [X] Critical user journeys are covered by Gherkin stories
• [X] Critical and brittle code paths are covered by unit tests

PR process

• [ ] PR has the correct target branch and milestone
• [ ] PR has 'needs review' or 'work-in-progress' label
• [ ] If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• [ ] If this is an important user-facing change, PR or related issue has a 'changelog' label
• [ ] If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions[bot]]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0a0.dev0_git.639.g3fc29b9d.pex
Windows Installer (EXE)	kolibri-0.16.0a0.dev0+git.639.g3fc29b9d-unsigned.exe
Debian Package	kolibri_0.16.0a0.dev0+git.639.g3fc29b9d-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0a0.dev0+git.639.g3fc29b9d-0.4.0.dmg
Android Package (APK)	kolibri-0.16.0a0.dev0+git.639.g3fc29b9d-0.1.0-debug.apk
TAR file	kolibri-0.16.0a0.dev0+git.639.g3fc29b9d.tar.gz
WHL file	kolibri-0.16.0a0.dev0+git.639.g3fc29b9d-py2.py3-none-any.whl