Flat after tie (0.9.6 regression)

Steps to reproduce bug
1. Open "tieFlat.mscz"
2. Click to select whole note
3. Press + to add a tie

Expected behavior: Flat in front of the first half note should now move to the next "Ab" note in the measure

Actual behavior: Flat in front of first half note disappears (as expected) but the next Ab doesn't have a flat sign in front

MuseScore version: r. 2713 nightly

(Operating System: Windows XP)

First reported by XavierJazz: http://musescore.org/node/4532