Closes when fallback audio codec none is selected

### Problem Description

Happens with Stable 12.20 and Beta 13.9

Choose a preset with fallback none, drop (or load from recent) the video into it and watch it disappearing :)

Does not close when source file has no subtitles embedded. Tried with MP4 files.

### What version of VidCoder are you running?

Beta 13.9 VelopackInstaller

### Encode Log

```text
No encode log necessary or possible.
```