fixed null reference exception in Token operator overload

Author: vlada-shubina

src/System.CommandLine/Parsing/Token.cs

@@ -66,14 +66,15 @@ internal Token(string? value, TokenType type, Symbol? symbol, int position)
         /// <param name="left">The first <see cref="Token"/>.</param>
         /// <param name="right">The second <see cref="Token"/>.</param>
         /// <returns><see langword="true" /> if the objects are equal.</returns>
-        public static bool operator ==(Token left, Token right) => left.Equals(right);
+        public static bool operator ==(Token? left, Token? right) => left is null ? right is null : left.Equals(right);
 
         /// <summary>
         /// Checks if two specified <see cref="Token"/> instances have different values.
         /// </summary>
         /// <param name="left">The first <see cref="Token"/>.</param>
         /// <param name="right">The second <see cref="Token"/>.</param>
         /// <returns><see langword="true" /> if the objects are not equal.</returns>
-        public static bool operator !=(Token left, Token right) => !left.Equals(right);
+        public static bool operator !=(Token? left, Token? right) => left is null ? right is not null : !left.Equals(right);
+
     }
 }