Fix rat pathfinding (#12951)

Fixes https://github.com/space-wizards/space-station-14/issues/12950

Content.Server/NPC/Systems/NPCSteeringSystem.cs

@@ -30,6 +30,7 @@ namespace Content.Server.NPC.Systems
         [Dependency] private readonly SharedInteractionSystem _interaction = default!;
         [Dependency] private readonly SharedMeleeWeaponSystem _melee = default!;
         [Dependency] private readonly SharedMoverController _mover = default!;
+        [Dependency] private readonly SharedPhysicsSystem _physics = default!;
 
         // This will likely get moved onto an abstract pathfinding node that specifies the max distance allowed from the coordinate.
         private const float TileTolerance = 0.40f;