actually free IDs on message clear

encompass-cs/Collections/TypedMessageStore.cs

@@ -113,6 +113,10 @@ namespace Encompass
 
         public override void Clear()
         {
+            foreach (var index in _indices)
+            {
+                _idManager.Free(index);
+            }
             _indices.Clear();
             foreach (var set in _entityToIndices.Values)
             {