[BUGFIX] Correct handling of ObjectStorage objects in PaginateController

The current implementation for getting paginated items from ObjectStorage
objects in TYPO3\CMS\Fluid\ViewHelpers\Widget\Controller\PaginateController
enforces null items if the count of objects is lower than the
itemsPerPage count. This patch calculates the correct count and returns
valid items only.

Resolves: #79559
Releases: master, 7.6
Change-Id: I5746d83120474d6246da949f67096459ed1076d7
Reviewed-on: https://review.typo3.org/51475


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jasmina Ließmann <code@frauliessmann.de>
Tested-by: Jasmina Ließmann <code@frauliessmann.de>
Reviewed-by: Christian Matthes
Tested-by: Christian Matthes
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Tested-by: Helmut Hummel <typo3@helhum.io>