Bar lines disappearing when hiding empty staves
If a bar line is extended over multiple instrument staves and the highest involved staff is not the first staff, the bar lines disappear in all involved staves, if the first involved staff is hidden via "hide empty staves".
Steps to reproduce:
1. Create a new score with some instruments.
2. Extend a bar line from a staff (not the highest staff) to the staff below.
3. Enter some notes in the lower involved staff, so that there is a system with notes only in the lower staff.
4. Click on "Hide empty staves".
In the example file, look at the second system.
Used MuseScore version: Nightly Build for Version 2.0.0, Revision 1b4d81d