pressure plate triggering when picking up item that fell from above

[MattWeiner]

A bundle of darts fell through a pit caused by a dying pit bloat. On the level below, the darts were on a pressure plate (undetected). On picking the darts up, the plate triggered a paralysis trap.

The usual behavior I see is that when an item is on a trigger, picking the item up does not trigger the trap. Though the only way I've seen this happen before is after throwing the item onto the trigger, so it has already set off the trap.

(Some edge cases: What if a monster carrying an item dies on a trigger, dropping the item? What if a monster carrying an item is polymorphed into a flying form, flies over the trigger without triggering the trap, and dies on that square, dropping the item?)

See brogue.roguelikelike.com/#viewRecording/BROGUECEV111-6297d2ff04d317dc9dd62e39

At turns 4550/4551 the pit bloat bursts, dropping the darts to the next level. Descend to next level at 4882. At 4889, picking up the darts triggers the paralysis trap..

[MattWeiner]

Thought of another couple edge cases, though probably one fix would handle them all: allied empowered monkey learns to fly, becomes discordant/hostile, steals item, dies while flying over trigger a vampire usually starts with an an item and when it transforms into bats does one of the bats wind up holding the item? so could the bat fly over a trigger and drop the item when it dies? vampires confuse me

[brturn]

Opened a PR to fix this (#534).

Checked that monsters dropping items on death or when becoming allied also works.