Do not show '-' for additional info which is not available for an item

I'm only backporting the removal of the '-', not the update for the
line number calculation in Icons View, because this is the safest part
of the patch and also the one that fixes the most annoying part of the
bug.

Thanks to Todd Jennings for the patch!
BUG: 304752
REVIEW: 106304
(cherry picked from commit 20b0cb68)