fix: fixes sending files to start a thread

[GleidsonDaniel]

Proposed changes

Currently, when trying to start a thread with an image or file, it was sent to the room and not to the thread. Another error was that as there was no thread created, the header said that the file would be sent to the room and not to the thread.
This PR fixes both of these errors.

Issue(s)

How to test or reproduce

• Send a message in the room and click the "Reply in thread" button.
• Within the "thread" try sending a image.

Screenshots

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

Jira: CORE-411