[FEATURE] Keep "new content element" icon visible if the column is empty

Resolves: #51480
Releases: 6.2
Change-Id: Ieaff9ddaf43e339979ecb5fff48678d28b9b0e61
Reviewed-on: https://review.typo3.org/23438
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring