Added code for stopping all downloads before quiting application
Corrected process of preparing items to show when items have been already cached
Removed sample of busy indicator
Upgraded version of used QML components
Commented out using of BusyIndicator.
If BusyIndicator is visible and running when application is closing it leads to crash.
Looks like https://bugreports.qt-project.org/browse/QTBUG-37995, but this defect reported as fixed in 5.3.2. However, migration to 5.3.2 didn't help. Need further investigation.