PowerWidget : Sound mode fix

Currently when you upgrade to a nightly that makes use of : http://review.cyanogenmod.com/#change,8643
You get a force close if previously you had the setting to say 4, or anything
greater than the current length of modes.

This attempts to address that issue.

Change-Id: I7de56191059ee4893b42a2c6bfd63f3d992bc589