Don't print exception message in HTML

Don't print exception message in HTML

The exception message is potentially influenced by user input and could thus be confusing (e.g. somebody could try to open a file like "Please send a mail to support@foo.com", and then the message would include that string.

It is thus reasonable to not show the exception message by default. Also for the browser view I added an `exit()` at the end, as otherwise the XML exception would be attached.