275|Bugfix: Crash when session was previously quit without exiting drawing mode.

Description of fix

Use sequences from the main scene instead of context ones. This is more reliable.

How to test it

1. Start a review session.
2. Enter advanced drawing mode
3. Without clicking "cancel drawing" nor "complete drawing", quit Stax
4. Re-run stax for the same review session

Checklist

Please check if your MR fulfills the following requirements:

• Build was run locally and any changes were pushed
• Lint has passed locally without error
• CHANGELOG.md has been updated
• Branch has been rebased on merge branch

FYI: @olivier.hoareau