Combine selected Mail messages into a new email

tell application "Mail"
    set selectedMessages to selection
    if (count of selectedMessages) is equal to 0 then
        display alert "No Messages Selected" message "Select the messages you want to collect before running this script."
    end if
    set theText to ""
    repeat with theMessage in selectedMessages
        set theText to theText & (content of theMessage) as string
    end repeat
    set theSubject to "Subject goes here"
    set theMessage to make new outgoing message with properties {subject:theSubject, content:theText, visible:true}
end tell