Changing preferences drops "Page View" dropdown to the default value

1. Change "Page View" dropdown to "Continuous view"
2. Open Preferences window
3. Click "Apply"

Result: the score is in a continuous view, but the dropdown indicates "Page View"
Expected result: actual view mode is synchronised with the dropdown control

The issue might be not so easy to resolve because it indicates the inconsistency between actual state of the view and related control. They must be synchronised all the time despite on the external changes to the control values or actual view switching. The synchronisation must be supported by internal C++/Qt mechanisms not relying on the possible user interactions.