Page with doktype 3 (external URL) and e-mail as URL could be shown directly (mailto:)
Imagine to create a page of doktype "3" (external URL) and an e-mail address is chosen to be the URL.
On rendering this page e.g. in a menu-structure in the Frontend, a regular link (index.php?id=nnn) is created. If someone clicks on that link, he get's a empty page and a location-header with the "mailto:firstname.lastname@example.org" string.
It would be better to prevent the empty page and have the "mailto:" set directly in the menu-structure (also with spam-protection etc.).
(issue imported from #M4758)