`/new-topic` redirects back to `/latest`, so the ember router considers this to be a 'refresh'. This triggers the `resetParams()` logic, which would cause the transition to abort, and the composer would never open.
This commit fixes the `resetParams()` logic so that it uses the default values, instead of setting everything to `null`. Therefore the transition is no longer aborted, and the composer opens successfully.
Unfortunately I have not been able to reproduce the issue in a QUnit test.