Changelog:

• Fix an uninitialized memory access, which could have led to NULL dereference or heap corruption in an out-of-memory situation.
• Fix a use-after-free when calling fluid_player_stop().
• Fix the MIDI player not outputting any sound after stopping and restarting the playback.

• Test sound output in qsynth with both alsa midi and jack_midi signals from my MIDI keyboard.