[BUGFIX] Switch to List module on root page leads to blank page

Reproducable only with admin account. Switch to Page module, go to root
page (id = 0), switch to List module => blank page. Works only on
root page.

Change-Id: I377bf20708631e81d2854645b18a1211889e6409
Releases: 6.0, 4.7, 4.6, 4.5
Resolves: #40781
Reviewed-on: http://review.typo3.org/14490
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader