Add TryQueueDeleteEntity (#5281)

Having to check deleted by hand up front is annoying.

Robust.Client/UserInterface/Controls/EntityPrototypeView.cs

@@ -33,10 +33,7 @@ public class EntityPrototypeView : SpriteView
 
         _currentPrototype = entProto;
         SetEntity(null);
-        if (_ourEntity != null)
-        {
-            EntMan.DeleteEntity(_ourEntity);
-        }
+        EntMan.DeleteEntity(_ourEntity);
 
         if (_currentPrototype != null)
         {
@@ -57,8 +54,6 @@ public class EntityPrototypeView : SpriteView
     protected override void ExitedTree()
     {
         base.ExitedTree();
-
-        if (!EntMan.Deleted(_ourEntity))
-            EntMan.QueueDeleteEntity(_ourEntity);
+        EntMan.TryQueueDeleteEntity(_ourEntity);
     }
 }

Robust.Shared/GameObjects/EntityManager.cs

@@ -468,6 +468,21 @@ namespace Robust.Shared.GameObjects
             ent.Comp4.LastModifiedTick = CurrentTick;
         }
 
+        public bool TryQueueDeleteEntity(EntityUid? uid)
+        {
+            if (uid == null)
+                return false;
+
+            if (Deleted(uid.Value))
+                return false;
+
+            if (!QueuedDeletionsSet.Add(uid.Value))
+                return false;
+
+            QueueDeleteEntity(uid);
+            return true;
+        }
+
         /// <summary>
         /// Shuts-down and removes given Entity. This is also broadcast to all clients.
         /// </summary>

Robust.Shared/GameObjects/EntitySystem.Proxy.cs

@@ -705,6 +705,13 @@ public partial class EntitySystem
         EntityManager.QueueDeleteEntity(uid);
     }
 
+    /// <inheritdoc cref="IEntityManager.TryQueueDeleteEntity(EntityUid?)" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected bool TryQueueDel(EntityUid? uid)
+    {
+        return EntityManager.TryQueueDeleteEntity(uid);
+    }
+
     #endregion
 
     #region Entity Spawning

Robust.Shared/GameObjects/IEntityManager.cs

@@ -153,6 +153,11 @@ namespace Robust.Shared.GameObjects
             where T3 : IComponent
             where T4 : IComponent;
 
+        /// <summary>
+        /// Tries to QueueDeleteEntity if the entity is not already deleted.
+        /// </summary>
+        public bool TryQueueDeleteEntity(EntityUid? uid);
+
         public void QueueDeleteEntity(EntityUid? uid);
 
         public bool IsQueuedForDeletion(EntityUid uid);