Fix glue puddle slowdown (#17260)

Content.Shared/Movement/Systems/SlowContactsSystem.cs

@@ -10,6 +10,8 @@ public sealed class SlowContactsSystem : EntitySystem
     [Dependency] private readonly SharedPhysicsSystem _physics = default!;
     [Dependency] private readonly MovementSpeedModifierSystem _speedModifierSystem = default!;
 
+    // TODO full-game-save
+    // Either these need to be processed before a map is saved, or slowed/slowing entities need to update on init.
     private HashSet<EntityUid> _toUpdate = new();
     private HashSet<EntityUid> _toRemove = new();
 
@@ -19,6 +21,7 @@ public sealed class SlowContactsSystem : EntitySystem
         SubscribeLocalEvent<SlowContactsComponent, StartCollideEvent>(OnEntityEnter);
         SubscribeLocalEvent<SlowContactsComponent, EndCollideEvent>(OnEntityExit);
         SubscribeLocalEvent<SlowedByContactComponent, RefreshMovementSpeedModifiersEvent>(MovementSpeedCheck);
+        SubscribeLocalEvent<SlowContactsComponent, ComponentShutdown>(OnShutdown);
 
         UpdatesAfter.Add(typeof(SharedPhysicsSystem));
     }
@@ -56,6 +59,16 @@ public sealed class SlowContactsSystem : EntitySystem
         component.WalkSpeedModifier = walkSpeed;
         component.SprintSpeedModifier = sprintSpeed;
         Dirty(component);
+        _toUpdate.UnionWith(_physics.GetContactingEntities(uid));
+    }
+
+    private void OnShutdown(EntityUid uid, SlowContactsComponent component, ComponentShutdown args)
+    {
+        if (!TryComp(uid, out PhysicsComponent? phys))
+            return;
+
+        // Note that the entity may not be getting deleted here. E.g., glue puddles.
+        _toUpdate.UnionWith(_physics.GetContactingEntities(uid, phys));
     }
 
     private void MovementSpeedCheck(EntityUid uid, SlowedByContactComponent component, RefreshMovementSpeedModifiersEvent args)
@@ -90,7 +103,6 @@ public sealed class SlowContactsSystem : EntitySystem
     private void OnEntityExit(EntityUid uid, SlowContactsComponent component, ref EndCollideEvent args)
     {
         var otherUid = args.OtherEntity;
-        if (HasComp<MovementSpeedModifierComponent>(otherUid))
         _toUpdate.Add(otherUid);
     }