fix 404 page not shown for paths with more than one slash

[jomapp]

We do not show the 404 page on the webapp correctly if paths that did not exist include more than one slash.
e.g. /test/test.

Test Notes:

• https://app.test.tuta.com/test/test/ should show the 404 page
• https://app.test.tuta.com/mail/test/ should not show the 404 page
• https://app.test.tuta.com/test/something/ should show the 404 page