[BUGFIX] Remove early return in PageTreeDataProvider

t3lib_tree_pagetree_Data_Provider does an early
return which makes it impossible to use the hook
which comes some lines later.

Change-Id: If65238527126b150664581d140d6d0761650fb8f
Fixes: #33761
Releases: 4.7, 4.6
Reviewed-on: http://review.typo3.org/8915
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Wouter Wolters
Reviewed-by: Stefan Galinski
Tested-by: Stefan Galinski
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch