Sharp not set after an accidental natural (0.9.6 regression)

If a note with a natural is followed by the same note but half-tone higher in pitch, a sharp is not set for this note unless the note with the natural is moved up and down.

STR:
1. Create a score e.g. in A major (3 sharps)
2. In Note Input Mode, press F and down to produce F natural
3. Press F again.

Actual results: the note in step 3 is F sharp in pitch, but lacks the accidental. As a workaround press left and move the first note up and down, then MuseScore will add a sharp to the second note.

This regression has been introduced by r2796.

MuseScore r2811 on Ubuntu 9.10 with Qt 4.6.1.