Don't attempt to use broken weapons in AI

apps/openmw/mwmechanics/aicombataction.cpp

@@ -102,7 +102,11 @@ namespace MWMechanics
         }
 
         if (item.getClass().hasItemHealth(item))
+        {
+            if (item.getClass().getItemHealth(item) == 0)
+                return 0.f;
             rating *= item.getClass().getItemHealth(item) / float(item.getClass().getItemMaxHealth(item));
+        }
 
         if (weapon->mData.mType == ESM::Weapon::MarksmanBow)
         {