ComposerServiceImpl creates incorrect incidents and error messages

Steps to reproduce:
1. Trigger one or more of the catch blocks under https://bitbucket.org/opencast-community/matterhorn/src/71c79545acc098150ce42dd2c77d71e8931921a1/modules/matterhorn-composer-ffmpeg/src/main/java/org/opencastproject/composer/impl/ComposerServiceImpl.java?at=develop&fileviewer=file-view-default#ComposerServiceImpl.java-246
2. Note that it creates log and incident reports about the audio file, not the video file.
3.

Actual Results:

Expected Results:

Workaround (if any):