Bugfix: clear_drawings doesn't work for dropped media

Description of fix

Added condition for medias at timeline's root.

How to test it

• Draw with annotate
• clear_drawings

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: @dddjef