Resolve "Project export broken when avatar is set"

What does this MR do?

Fixes typo on AvatarUploader#absolute_path should have passed an upload and not the model.avatar.

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #51318 (closed)