The navigator and the "display position" are not updated when deleting all measures
Create a new score and ensure that there are at least 2 pages (for example 200 measures). The navigator at the bottom shows two little thumbnails.
Go to the second page. Do "Ctrl+A" to select all measures and "Ctrl+Delete" to delete them.
The score now has only one (blank) page, but the navigator still displays two thumbnails. Also, the "display position" is not updated. All we see is a gray area.
The navigator should display only one thumbnail and the "display position" should be set to the beginning of the only (blank) page left.
There's no bug if we don't select all measures. For example, select all measures but the first one, go to the second page and do "Ctrl+Delete".
The navigator is updated and the "display position" is correctly set to the beginning of the first page.
MuseScore e4004d6 on Xubuntu 14.10.