Fixed validation

Author: sakno

src/DotNext/Threading/Tasks/Conversion.cs

@@ -73,7 +73,12 @@ public static async Task<TOutput> Convert<TInput, TOutput>(this Task<TInput> tas
     /// <param name="task">The task to convert.</param>
     /// <typeparam name="T">The type of the task.</typeparam>
     /// <returns>The task that never throws an exception. Instead, the <see cref="Result{T}"/> contains an exception.</returns>
-    public static AwaitableResult<T> SuspendException<T>(this Task<T> task) => new(task);
+    public static AwaitableResult<T> SuspendException<T>(this Task<T> task)
+    {
+        ArgumentNullException.ThrowIfNull(task);
+
+        return new(task);
+    }
 
     /// <summary>
     /// Suspends the exception that can be raised by the task.