fix #26451: state after microtonal accidental

Microtonal accidentals play back as naturals and did in 1.X as well; now they also act like naturals in terms of setting the accidental state for the measure.  So subsequent notes act like the natural is now in effect, thus cancelling any earlier accidental or key signature.  See discussion in issue thread and also here:

http://musescore.org/en/node/26296