[BUGFIX] AbstractTreeView correct permission handling with non pages

AbstractTreeView now checks correctly, if a user has permission
to access elements even if they are not pages.

Without this change it was always assumed that the "uid" of the record
is the page uid. However, that is only valid for pages.

Change-Id: I4dd4970fb529ac6ab6f3c79d993456feed225fea
Resolves: #63047
Releases: master, 6.2
Reviewed-on: http://review.typo3.org/37034


Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Andreas Fernandez <andreas.fernandez@aspedia.de>
Tested-by: Andreas Fernandez <andreas.fernandez@aspedia.de>