Fix iterator not working with fixed terms

src/gaemstone/ECS/Iterator.cs

@@ -51,8 +51,9 @@ public unsafe partial class Iterator
 	{
 		fixed (ecs_iter_t* ptr = &Value) {
 			var size    = (ulong)Unsafe.SizeOf<T>();
+			var isSelf  = ecs_field_is_self(ptr, index);
 			var pointer = ecs_field_w_size(ptr, size, index);
-			return new Span<T>(pointer, Count);
+			return new(pointer, isSelf ? Count : 1);
 		}
 	}