Stop empty audio system filters from playing sounds for all players (#…

…5444)

* Fix audio system empty filter bug

* The nullable attributes are lying

RELEASE-NOTES.md

@@ -43,6 +43,7 @@ END TEMPLATE-->
 
 ### Bugfixes
 
+* Fixed filtered AudioSystem methods playing a sound for all players when given an empty filter.
 * Fixed equality checks for `MarkupNode` not properly handling attributes.
 * Fixed `MarkupNode` not having a `GetHashCode()` implementation.
 * Fixed a PVS error that could occur when trying to delete the first entity that gets created in a round.

Robust.Server/Audio/AudioSystem.cs

@@ -66,32 +66,26 @@ public override void SetMapAudio(Entity<AudioComponent>? audio)
 
     private void AddAudioFilter(EntityUid uid, AudioComponent component, Filter filter)
     {
-        var count = filter.Count;
+        DebugTools.Assert(component.IncludedEntities == null);
+        component.IncludedEntities = new();
 
-        if (count == 0)
+        if (filter.Count == 0)
             return;
 
         _pvs.AddSessionOverrides(uid, filter);
-
-        var ents = new HashSet<EntityUid>(count);
-
         foreach (var session in filter.Recipients)
         {
-            var ent = session.AttachedEntity;
-
-            if (ent == null)
-                continue;
-
-            ents.Add(ent.Value);
+            if (session.AttachedEntity is {} ent)
+                component.IncludedEntities.Add(ent);
         }
-
-        DebugTools.Assert(component.IncludedEntities == null);
-        component.IncludedEntities = ents;
     }
 
     /// <inheritdoc />
     public override (EntityUid Entity, AudioComponent Component)? PlayGlobal(string? filename, Filter playerFilter, bool recordReplay, AudioParams? audioParams = null)
     {
+        if (string.IsNullOrEmpty(filename))
+            return null;
+
         var entity = SetupAudio(filename, audioParams);
         AddAudioFilter(entity, entity.Comp, playerFilter);
         entity.Comp.Global = true;