Fix bug with 'Up' and 'Down' and empty selection
Fix bug with 'Up' and 'Down' and empty selection

Using the 'Up' or 'Down' buttons in the organizer with no item selected would raise an exception.
Using the 'Top' or 'Bottom' buttons would do nothing, but _moveToTop() and _moveToBottom() also got their fancy showInfo anyway.
luoliyan/incremental-reading-for-anki,luoliyan/incremental-reading-for-anki