Dupes are trying to fight nothing?

All of my dupes are in a constant state of attacking a creature, though there is nothing to attack.  They won't move or do anything else unless I specifically tell them to move somewhere.  When I tell them to move, they will go there and continue to stand still.  Eventually they all had to use the bathroom and ended in a clump at the bathrooms.

I'm sure they will all starve themselves in their attempt to kill nothing.

Beyond.sav