[BUGFIX] Erroneous date sorting in File List

The sorting by date fails in the Filelist module when more
than 9 files with the same date are found since the numerical
suffix used to avoid overwriting existing entries in the
sorting array is not properly padded.

Fixes: #59458
Releases: 6.2, 6.1
Change-Id: I2c80a00dd1692b0987da3d461cc5a21fcea4c97d
Reviewed-on: https://review.typo3.org/30711
Reviewed-by: Francois Suter
Tested-by: Francois Suter