Added null check

src/Renci.SshNet/Abstractions/ThreadAbstraction.cs

@@ -25,6 +25,9 @@ namespace Renci.SshNet.Abstractions
         /// <param name="action">The action to execute.</param>
         public static void ExecuteThread(Action action)
         {
+            if (action == null)
+                throw new ArgumentNullException("action");
+
 #if FEATURE_THREAD_THREADPOOL
             System.Threading.ThreadPool.QueueUserWorkItem(o => action());
 #elif FEATURE_THREAD_TAP