[BUGFIX] Invalid use of array_shift() in t3lib_div

PHP Runtime Notice: Only variables should be passed by reference.

Change-Id: Ib1e9af4b58202f085d1afbba2b9bd0b288a8ef58
Fixes: #30056
Releases: 4.6
Reviewed-on: http://review.typo3.org/5083
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers