[BUGFIX] Remove empty brackets when configuration type is unknown

When reenable the default configuration field rendering it might be happen
that type description es empty and only the brackets are shown. Those
could be dropped.

Change-Id: I09b30558832a58092fdcc2262bb2278b70cd04ea
Fixes: #43043
Releases: 6.0
Depends: Ic49c9b19a7f8f1795889f17ed5c1efa364dfd9b9
Reviewed-on: http://review.typo3.org/16505
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Reviewed-by: Stefan Neufeind
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer