Attached files stay in the create post UI

[maxceem]

After we create a post with attachments and open a dialog to create another new post, the previously attached files are still listed there.

See video https://monosnap.com/file/gEntEZedkKPGW7ZqobJzdXss9M8efJ

Follow up from #3031

[vikasrohit]

Working fine. Closing.