[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: I6f9def862a4398ea0e8972b395d5a58a4dc4a241
Fixes: #44481
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/17502
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert