URL with incorrect format can be added to external links

Steps to reproduce:

1. Log in as admin
2. Administration mode is enabled
3. Open External link editor
4. Click Add button
5. Fill form with valid data in Title and incorrect data for URL link field (mail@mail.ru, text, <script>Alert(Hi!)</script>, SELECT * FROM USERS)
6. Click Save button

AR: The link was successfully added to external links.
ER: Error message occurs that the link must be inputted in "URL" format.