Early in, a bowl gets thrown at a force field in the 'new brig', and bounces off. Later, The Doctor is holding a Padd and walks through a Force Field in the Med Bay. Though The Doctor is a Hologram, the Padd shouldn't have been able to pass through the force field.
Even though Iko is known to be violent, The Doctor leaves data pads, tricorders and other equipment next to him in sick bay. The warden wouldn't even let them have spoons.
The second time Iko is in sickbay, there are no force fields around him. True, he is unconscious at the time, but the Doctor knows little about his anatomy and, since he is known to be violent, all simple precautions should be taken.