Get a pointer to the user data for the current music hook.
Defined in <SDL3_mixer/SDL_mixer.h>
void * Mix_GetMusicHookData(void);(void *) Returns pointer to the user data previously passed to Mix_HookMusic.
This returns the arg pointer last passed to Mix_HookMusic(), or NULL if that function
has never been called.
This function is available since SDL_mixer 3.0.0.