[BUGFIX] TCA 'group' selectedListStyle with 'width' breaking layout

The problem came from a row of icons which was always rendered below
the select list with a hardcoded width of "250px", regardless if there
was content or not. Solution is not to render this icon row if there are
no icons, thus allowing the select list to be reduced in width.

Releases: 6.2, 6.1, 6.0
Resolves: #50707
Change-Id: I23520c1c547de1155091e38c69013a18fed9e559
Reviewed-on: https://review.typo3.org/23391
Reviewed-by: Kai Ole Hartwig
Tested-by: Kai Ole Hartwig
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn