Wav export does not use latest sound settings

1. Create flute score
2. Add a few notes
3. Display > Mixer
4. Change the flute sound to organ
5. File > Save As... and choose "wav" export

Expected behavior: Wav file should sound like organ

Actual behavior: Wav file sounds like flute

Workaround: File > Save before you export to "wav".

(Tested using 0.9.5, Windows XP)

First reported by patrickbieri: http://musescore.org/en/node/2414