AppleScript for Mail附件在Mojave beta 10中不起作用

Question

以下脚本在High Sierra中可以正常运行，但是无法将文件附加到Mojave中的邮件消息中。邮件标题，内容和收件人设置正确，但附件设置不正确。有什么想法吗？

set theAttachment to (choose file with prompt "Select file for attachment...")

tell application "Mail"

    set theMessage to make new outgoing message with properties {visible:true, subject:"File Attachment Test", content:"Some test content" & linefeed & linefeed}

    tell theMessage
        make new to recipient at end of to recipients with properties {name:"John Doe", address:"johndoe@domain.com"}
    end tell

    tell content of theMessage
        make new attachment with properties {file name:theAttachment} at after last paragraph
    end tell

end tell