[Bug] Restored urls get lost on app exit

[fidel]

Describe the bug
In case a user stored the content of the todo list on app exit, they get restored on next app starts.
If the user then quits the app again - media-dupes is not asking if it should restore the urls again on the next app launch

Expected behavior
Should ask again to store the content of the todo list

Desktop (please complete the following information):

• OS: linux
• media-dupes version: 0.7.0

[fidel]

bonus: based on #102 - if an items is removed from todo-list and the todo-list is then empty - we need to update the globalobject as well.