Could not handle empty nested message

When we load an EML using Aspose.Email, then convert it to MapiMessage, it will throw NULL exception.
After I checked the email, I found that the message has a nested message. But the nested message is empty.
Could you please fix the bug so empty nested email can be processed?

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MailMessage mailMsg = MailMessage.load(bis, mailLoadOption);
MapiMessage.fromMailMessage(mailMsg, MapiConversionOptions.getUnicodeFormat());   

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java.lang.NullPointerException
    at com.aspose.email.MailMessage.a(Unknown Source)
    at com.aspose.email.MailMessage.a(Unknown Source)
    at com.aspose.email.MailMessage.<init>(Unknown Source)
    at com.aspose.email.MailMessage.b(Unknown Source)
    at com.aspose.email.MailMessage.a(Unknown Source)
    at com.aspose.email.MapiMessage.a(Unknown Source)
    at com.aspose.email.MapiMessage.b(Unknown Source)
    at com.aspose.email.MapiMessage.a(Unknown Source)
    at com.aspose.email.MapiMessage.a(Unknown Source)
    at com.aspose.email.MapiMessage.fromMailMessage(Unknown Source)
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