Consider that the topic of a room has been removed when it's blank.

[bmarty]

Content

Motivation and context

Closes #4206

Screenshots / GIFs

Tests

• In a room, set the topic to ""
• observe the rendering on the timeline.

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes have been tested on an Android device or Android emulator with API 24
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly define what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• You've made a self review of your PR

[github-actions]

📱 Scan the QR code below to install the build (arm64 only) for this PR.

If you can't scan the QR code you can install the build via this link: https://i.diawi.com/7MTAhT

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.19%. Comparing base (ebfb47e) to head (3a6ba44).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4209   +/-   ##
========================================
  Coverage    80.19%   80.19%           
========================================
  Files         2022     2022           
  Lines        53271    53271           
  Branches      6443     6443           
========================================
  Hits         42723    42723           
  Misses        8330     8330           
  Partials      2218     2218           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.