[Bug?] No output when the audio duration exceed 7200s

## Description

The audio(.mp3) duration is more than 1 hour, when I use default command
`spleeter separate -p spleeter:2stems -o output live3.mp3`
it can work and generate two 7min separated files in output,

but when I set `-d 7200 `, the processed audio did not generated even no error appear
` spleeter separate -p spleeter:2stems -d 7200 -o output live3.mp3`


## Environment

| | |
| ----------------- | ------------------------------- |
| OS | Windows |
| Installation type | pip |
| Hardware spec | 3060ti/ i7-9700kf / etc ... |

## Additional context

Reproduce the issue with the two documented `spleeter separate` commands, comparing the default behavior with `-d 7200` on a long MP3 under the stated Windows and pip environment. Trace the command's duration handling and confirm done when the `-d 7200` invocation generates the expected separated output or reports a clear error.

Written by the indexing model from the issue text.