Fix element call crash when resuming from notification

[bmarty]

Content

Ensure that when the call is resume when clicking on the notification, the app does not crash.

Seems that this is a regression from #3833.

Motivation and context

Fix #3905

Screenshots / GIFs

Tests

• Step 1
• Step 2
• Step ...

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes have been tested on an Android device or Android emulator with API 23
• 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
• Pull request includes a sign off
• You've made a self review of your PR

[bmarty]

Not strictly necessary, but should prevent future crash...

[github-actions]

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[sonarcloud]

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

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 82.99%. Comparing base (5a6525a) to head (0a1c441).
Report is 11 commits behind head on develop.

Files with missing lines	Patch %	Lines
...droid/features/call/impl/ui/ElementCallActivity.kt	0.00%	15 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3926      +/-   ##
===========================================
- Coverage    83.00%   82.99%   -0.01%     
===========================================
  Files         1788     1788              
  Lines        45210    45213       +3     
  Branches      5335     5337       +2     
===========================================
  Hits         37526    37526              
- Misses        5810     5813       +3     
  Partials      1874     1874              

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