More power nullability (#3070)

Content.Server/GameObjects/EntitySystems/Power/PowerApcSystem.cs

@@ -0,0 +1,28 @@
+#nullable enable
+using System.Collections.Generic;
+using Content.Server.GameObjects.Components.NodeContainer.NodeGroups;
+using Content.Server.GameObjects.Components.Power.ApcNetComponents;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects.Systems;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    [UsedImplicitly]
+    internal sealed class PowerApcSystem : EntitySystem
+    {
+        public override void Update(float frameTime)
+        {
+            var uniqueApcNets = new HashSet<IApcNet>(); //could be improved by maintaining set instead of getting collection every frame
+            foreach (var apc in ComponentManager.EntityQuery<ApcComponent>(false))
+            {
+                uniqueApcNets.Add(apc.Net);
+                apc.Update();
+            }
+
+            foreach (var apcNet in uniqueApcNets)
+            {
+                apcNet.Update(frameTime);
+            }
+        }
+    }
+}