AuthenticationResults.TryParse throws if string ends in header.from=

[The-Nutty]

Describe the bug
When passing authentication results like the following test.com; dkim=none (message not signed) header.d=none; test.com; dmarc=none action="none" header.from= (generated by office 365) the following line of code will throw (as opposed to parse successfully as i think it should or fail saliently and return false)

            Console.WriteLine(AuthenticationResults.TryParse(Encoding.UTF8.GetBytes((string) "test.com; dkim=none (message not signed) header.d=none; test.com; dmarc=none action=\"none\" header.from="), out var a));

Platform (please complete the following information):

• OS: Windows
• .NET Runtime: core 3.1
• MimeKit Version: tested 2.7 and 2.8

To Reproduce
Run the code sample in the description, will throw the following exception

Unhandled exception. System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at MimeKit.Cryptography.AuthenticationResults.SkipPropertyValue(Byte[] text, Int32& index, Int32 endIndex, Boolean& quoted)
   at MimeKit.Cryptography.AuthenticationResults.TryParseMethods(Byte[] text, Int32& index, Int32 endIndex, Boolean throwOnError, AuthenticationResults authres)
   at MimeKit.Cryptography.AuthenticationResults.TryParse(Byte[] text, Int32& index, Int32 endIndex, Boolean throwOnError, AuthenticationResults& authres)
   at MimeKit.Cryptography.AuthenticationResults.TryParse(Byte[] buffer, AuthenticationResults& authres)

Expected behavior
Passes without error

[jstedfast]

Thanks! Should be fixed now.