Bug (reproducable): Crash when filtering empty enemies list (Shift+V)

Go somewhere where there are items visible but no creatures
bring up the “look around” list (Shift+V)
go to the empty enemy list
try and filter

NOTE: crash does not occur when filtering empty items list, only on the enemies list

Tested on:
0.A Stable
0.A Experimental 6/2 (bc1cecd)