Corrected output for filtered Quizzes and Lessons

[radinamatic]

Summary

'No results' string for filtered Quizzes displays properly:

string-fix-quizzes.mp4

There is probably a more elegant way of fixing the second reported issue, but seems to be working OK now 🙂
On top of the 'No results' not being displayed for not visible lessons, it was displaying for visible ones even when there are no lessons at all, below the 'You do not have any lessons' message.

Before	After
https://github.com/learningequality/kolibri/assets/1457929/32cede85-7bd0-4e47-b40e-ab97da45cac1	https://github.com/learningequality/kolibri/assets/1457929/bcdbb015-f039-482a-9053-5eb9e744760b

There may still be an underlying loading issue (brief flash of 'No results' until the lesson is loaded and appears in the table), but is probably out of the scope of this PR and definitely above my pay grade 😅

References

Fixes #11310

…

Reviewer guidance

Change the status of the quizzes (start/end) and lessons (visible/not visible), and check if the 'No results' message is displayed properly for all filtered cases.

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[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0b6.dev0_git.23.g0f8f1ab7.pex
Windows Installer (EXE)	kolibri-0.16.0b6.dev0+git.23.g0f8f1ab7-unsigned.exe
Debian Package	kolibri_0.16.0b6.dev0+git.23.g0f8f1ab7-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b6.dev0+git.23.g0f8f1ab7-0.3.0.dmg
Android Package (APK)	kolibri-0.16.0b6.dev0+git.23.g0f8f1ab7-0.1.0-debug.apk
TAR file	kolibri-0.16.0b6.dev0+git.23.g0f8f1ab7.tar.gz
WHL file	kolibri-0.16.0b6.dev0+git.23.g0f8f1ab7-py2.py3-none-any.whl

[pcenov]

LGTM - let's further discuss and report separately any additional improvements which can be made such as the brief flash of 'No results' and the correct position of the Status filter :)!

[MisRob]

Kudos @radinamatic :)! Changes are looking good to me.

This is not blocking, just a suggestion how we could tweak naming and organization of conditions to improve readability. It took me some time to make all the connections due to unclear naming, the number of negations and having conditions at various places. This was something present before your update though - it's up to you if you'd like make these changes.

Template:

<p v-if="showNoResultsLabel">{{ coreString('noResultsLabel') }}</p>

JavaScript:

  hasVisibleLessons() {
    return this.activeLessonCounts.true
  },
  hasNonVisibleLessons() {
    return this.activeLessonCounts.false
  },
  showNoResultsLabel() {
    if (!this.lessons.length) {
      return false
    }
    if (this.filterSelection.value === 'filterLessonVisible') {
      return !this.hasVisibleLessons
    }
    if (this.filterSelection.value === 'filterLessonNotVisible') {
      return !this.hasNonVisibleLessons
    }
  },

[radinamatic]

Thank you @MisRob for suggestions on naming improvements (and @marcellamaki for last mile support), all done! 🙏🏽