Dropped items do not sustain terrain damage

[Frumple]

As per title. From attached save, simply aim summon monster I at a fiery curtain square until something with an inventory is summoned and promptly dies. Their equipment will remain, instead of disappearing as intended.

[RMTEW FULL NAME]

Terrain effects, like per turn or landing damage, only apply to creatures. Extending this to all items would be prohibitive. Fixing this requires some thought.