Fix possible NPEs
Jump over past lectures in list also in onResume()
Favorites list: Ask for confirmation before deleting all favorites
Hide delete action if favorites list is empty.

Hack: Pass confirmation dialog ID back to listener to
differentiate between different dialogs in one acitivity. Better solution
would be to pass a listener to the DialogFragment, but those cannot
be put into a bundle via setArguments. :-/
Fix successful return from XML parser with missing closing tag
bump version to 1.30.3