Mix_MusicDuration issues.

[CicTec]

Hi,
It seems that the indicated function has several issues.

1. Using Mix_MusicDuration with a Mix_Music object, this returns correct values for MP3 and OGG formats, while incorrect values for MIDI (for example a tested file should return 186 and returns 4294966)
2. Using MixMusicDuration with NULL parameter, it should return the duration of the music being played, instead it returns the correct value for MP3 and OGG as point 1, while for MIDI it returns -1.

The version used is SDL 2.8.0, while the tests are carried out on the Windows 10 operating system.

[bilhox]

I'm leaving a message here since I also have the same issue with WAV format returning ~24300s. I'm on Windows 11.