Do not report "record not found" as a failure for an unexpected reason

[kspurgin]

See the CSV attached to #176 for an example of this error.

1. CheckMediaService specifically raises a "record not found" message, so it is an expected thing that should be handled with better feedback.
2. I think I would pass it to feedback as a warning, not an error. This activity exists to check derivatives on existing media. The fact that a Media Handling record doesn't exist is kind of incidental/tangential to that. Possibly of interest, but not really what this should be having dataitem/action level errors over.