Adding organ parts after score creation causes incorrect cross-staff barlines

This is not specific to organ beaming, as I discovered this while working on #112361: Add 4-hands piano template and I originally thought it was something wrong with my 4-handed piano entry in instruments.xml. It affects both 2.0.3 and 3.0-dev.

Issue description: if you add an instrument that has multiple staves but the barline is not supposed to go through all of them (such as an organ or a 4-handed piano) after the score has been created, the barline goes through all the staves. You can edit it as normal after it's been added, so it's not a showstopper bug.

If you add these instruments during score creation, the barlines only cross the staves they're supposed to, as specified in instruments.xml. Adding these instruments after score creation should function the same way.