[TASK] Suppress mount point resolving if there are none

BE admins without mountpoints set have value '0' in
$this->groupData['webmounts']. If this is checked additonally
to empty string, some 'where uid=0' database calls can be suppressed.

Resolves: #86272
Releases: master
Change-Id: I4142034c3d3fac3c9319649fd39200da7955a8db
Reviewed-on: https://review.typo3.org/58290


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>