am 45dc4f82: am 493941b8: Allow creation of an audio effect on a session with no audio tracks.

Merge commit '45dc4f82a00e52b12389b22a7cfbbee5609e8e28'

* commit '45dc4f82a00e52b12389b22a7cfbbee5609e8e28':
  Allow creation of an audio effect on a session with no audio tracks.