[BUGFIX] Use array in check for new CE button

After #44470 the content elements in a column are stored in an array.
Checks for the new content element button, etcetera must check that
array instead of counting the elements in the query result that was used
before.

Change-Id: Iea75afd343db82a4950b4a9b7587177940398b2b
Fixes: #44481
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/17503
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert