Trill line position not saved (regression)

1. From the lines palette drag a trill (with the wiggly line) on to the score
2. Move the trill to a custom height above the staff (anything other than the default)
3. Save and reload score

The trill line should be in the custom position. Instead it returns to the default location. This behavior is also evident in the Bach-bc2 demo score.

First reported by KevinGregory: http://musescore.org/en/node/1850

(Tested using r. 1869, Windows XP)