Frontend: Main window: temporary fix regarding double-deletion: make sure the displayed document list is always up-to-date after each removal

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Frontend: Scan animation: When scan chunk are reduced, if their size reach 0, don't bother taking them into account at all

Signed-off-by: Jerome Flesch <jflesch@gmail.com>