Fix crash in message composer when room is missing

[jonnyandrew]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

• Handle a missing room safely when starting the message composer
• Hide the message composer UI when the room is missing
• Hide the voice recorder UI when the room is missing

Motivation and context

This error was seen before but has been reintroduced during refactoring.

• see Fix crash when opening an unknown room #6978

Screenshots / GIFs

Before	After
N/A

Tests

• Manually force Session.getRoom() to return null.
• Open a room
• Verify no crash and UI looks correct

Tested devices

• Physical
• Emulator
• OS version(s): Android 13

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• 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
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

0.0% Coverage
0.0% Duplication

[bmarty]

Thanks for fixing (again!) this issue.