When sharing a file or folder, the optional message will trigger an error if the user includes a URL in the message text. Instead of just validating the message body in context, the validation cancels the entire sharing popup interface and all of the email addresses that the user carefully entered and the entire message body that the user carefully crafted is lost. Why not just prompt the user to not type a URL and leave the sharing popup interface intact for correction? Also, an email address included in the message body is apparently considered a URL, which is not clear from the error.