[TYPO3-project-4-3] alt_intro.php

[Steffen Kamper]

Hi,

alt_intro.php is a sys extension 'about_modules'. It's a bit strange as 
it's callable even if the sys_ext is deinstalled. Try yourself: having 
it as startup modules, deinstall it and logout/login.

So i suggest 2 things:
1) check in EM when you try to deinstall if ext is used as startup 
modules, prevent if it'S set. This is nit enough, other users may have 
it in startup.

2) if about_modules is deinstalled, return blank document in alt_intro

vg Steffen