Fixed regression

Author: sakno

src/DotNext.Threading/Threading/CancellationTokenMultiplexer.CTS.cs

@@ -4,7 +4,7 @@ namespace DotNext.Threading;
 
 partial class CancellationTokenMultiplexer
 {
-    private sealed class PooledCancellationTokenSource : LinkedCancellationTokenSource
+    private sealed class PooledCancellationTokenSource : LinkedCancellationTokenSource, IResettable
     {
         private const int Capacity = 3;
         private (CancellationTokenRegistration, CancellationTokenRegistration, CancellationTokenRegistration) inlineList;
@@ -56,8 +56,9 @@ public ref CancellationTokenRegistration this[int index]
             }
         }
 
-        public void Clear()
+        public void Reset()
         {
+            tokenCount = 0;
             inlineList = default;
             extraTokens?.Clear();
         }

src/DotNext.Threading/Threading/CancellationTokenMultiplexer.Scope.cs

@@ -111,7 +111,7 @@ private static async ValueTask ReturnAsync(CancellationTokenMultiplexer multiple
 
         private static void Return(CancellationTokenMultiplexer multiplexer, PooledCancellationTokenSource source)
         {
-            source.Clear();
+            source.Reset();
             if (source.IsCancellationRequested)
             {
                 source.Dispose();

src/DotNext.Threading/Threading/CancellationTokenMultiplexer.cs

@@ -85,6 +85,7 @@ private PooledCancellationTokenSource Rent()
     private PooledCancellationTokenSource Rent(ReadOnlySpan<CancellationToken> tokens)
     {
         var source = Rent();
+        Debug.Assert(source.Count is 0);
 
         foreach (var token in tokens)
         {