Prevents errors on section deletion

Summary

Properly redirects when deleting a section
Cleans up section title TODOs.

References

Fixes #12332 I think this fixes the section_title part of #12294 as well - checking in with @LianaHarris360 and will back my changes out if she has done the fix already

Reviewer guidance

Delete a section, ensure that you navigate to the previous section and don't see any errors in the console

Testing checklist

[ ] Contributor has fully tested the PR manually
[ ] If there are any front-end changes, before/after screenshots are included
[ ] Critical user journeys are covered by Gherkin stories
[ ] 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

Asset type	Download link
PEX file	kolibri-.pex
Windows Installer (EXE)	kolibri-0.17.0a0.dev0+git.125.g6fd1a1f3-windows-setup-unsigned.exe
Debian Package	kolibri_0.17.0a0.dev0+git.125.g6fd1a1f3-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.17.0a0.dev0+git.125.g6fd1a1f3-0.4.2.dmg
Android Package (APK)	kolibri-0.17.0a0.dev0+git.125.g6fd1a1f3-0.1.3-debug.apk
TAR file	kolibri-0.17.0a0.dev0+git.125.g6fd1a1f3.tar.gz
WHL file	kolibri-0.17.0a0.dev0+git.125.g6fd1a1f3-py2.py3-none-any.whl

learningequality / kolibri

Prevents errors on section deletion #12363