hrydgard/ppsspp — pull request #2167 by oioitff (2013-06-09 13:17:32+00:00)
Title: Improve Atrac id generating and fix crash.

It may fix #2155 and some other crash.
The crash may happens as following:

AtracID = 0; bmg playing
AtracID = 1; voice; release;
AtracID = 2; voice; release;
....
AtracID = 255; voice; release;
AtracID = 0; crash ( already exists)
And a valid atracID in a real PSP seems only to be 0 ~ 6 from uofw.