fix bz623 - 'D' when not carrying anything

fix bz623 - 'D' when not carrying anything

With menustyle set to "full" or "partial", using 'D' when not
carrying anything gave no feedback.  (Modes "traditional" and
"combination" give "you have nothing to drop" via ggetobj().)

Also, there's no need to reset in-progress armor removal, lock
picking, or trap setting if you don't actually drop anything.
The inventory they're set to operate on or with stays intact.