[BUGFIX] Separators shown in explicit allow/deny section

The explicit allow/deny section of backend user groups (be_groups)
render separators (--div--) in the backend which need to be skipped.

Change-Id: Iac578d43a7a561618d095819b9d667c613621f2b
Resolves: #82379
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/54009


Reviewed-by: Simon Praetorius <simon@praetorius.me>
Tested-by: Simon Praetorius <simon@praetorius.me>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>