Unable to Unrar due to non-ASCII Characther

### Configuration
- Keka version: 1.2.54
- macOS version: 10.14.6

### Describe the bug
The RAR file has been sucessfully tested for its integrity using the unrar CLI version. So, the file should not be broken.
Unfortunately, Keka is unable to unrar a RAR file that include, what I'd call, “non-conventional” characters. Should I say “non-ASCII”? Anyway, this seems to be a character issue.

Or maybe Keka recognizes the non-ASCII characters as “weird” words, but can't create them on disk when trying to extract the archive.

The Keka UI says it in French, so I post in French:
```
Code erreur 2 en utilisant "7zz"
Erreur fatale
```

### To Reproduce
Steps to reproduce the behavior:
1. Try to unrar a file containing accents or strange character.
2. Error is as follows:
```
Code erreur 2 en utilisant "7zz"
Erreur fatale
```

### Expected behavior
Keka should unrar any non-malformed RAR file without issue.

### Screenshots
(N.A.)

### Additional context
If you'd like a log, tell me, step-by-step how to do activate as I don't know which option to activate in the “Help > Débogage” menu