Grader fails to grade if the submission filename contains nonstandard ASCII characters

e.g.: `Nirnamaâ¦.cpp`

```
ERROR [2024-10-25 13:37:50,482] [JIDGRAD0GrF4rEntpcIsSlg4eXe]: Grading failed!
! java.nio.file.InvalidPathException: Malformed input or input contains unmappable characters: ????.cpp
```