1) Start SB on Mac
2) File -> New to create a second blank document
3) Drop a component on document #1 and #2
4) Exit using Scene Builder -> Exit Scene Builder
5) Confirmation dialog appears for Document #1
6) Click on Cancel
7) Confirmation dialog appears for Document #2
    => BUG : it should not appear since we clicked on Cancel
8) Click on Cancel
    => SB does not exit
    => GOOD : exit operation has been cancelled
    => BAD : cancelling exit operation requires to click a Cancel button for each dirty document