fix ClientGameStateManager bug (#3727)

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -462,6 +462,7 @@ namespace Robust.Client.GameStates
 
             foreach (var entity in system.DirtyEntities)
             {
+                DebugTools.Assert(toRemove.Count == 0);
                 // Check log level first to avoid the string alloc.
                 if (_sawmill.Level <= LogLevel.Debug)
                     _sawmill.Debug($"Entity {entity} was made dirty.");
@@ -521,6 +522,7 @@ namespace Robust.Client.GameStates
                 {
                     _entities.RemoveComponent(entity, comp);
                 }
+                toRemove.Clear();
 
                 // Re-add predicted removals
                 if (system.RemovedComponents.TryGetValue(entity, out var netIds))

Robust.Shared/Utility/RemList.cs

@@ -13,6 +13,7 @@ namespace Robust.Shared.Utility
     public struct RemQueue<T>
     {
         public List<T>? List;
+        public int Count => List?.Count ?? 0;
 
         public void Add(T t)
         {
@@ -25,6 +26,11 @@ namespace Robust.Shared.Utility
             return new(List);
         }
 
+        public void Clear()
+        {
+            List?.Clear();
+        }
+
         public struct Enumerator : IEnumerator<T>
         {
             private readonly bool _filled;