Previously entered music corrupted when adding and moving up new instrument

1. Create new piano score
2. Enter some music in both staves
3. Add new instrument and move it up to be the new top system
(in one step without leaving the dialog!)

After this the previously entered music of the piano part is mixed up on the new instrument and the piano staves.

This does not happen when adding the new instrument, leaving the dialog window, going back to the "Instuments" dialog and move up the newly created instrument in a second step.

Using 7108e51 on Mac OS X 10.9.4