[BUGFIX] Fix height of the modal content

Fix height of the modal content to avoid misbehavior in IE11.

Resolves: #81232
Releases: master, 8.7
Change-Id: I302915e1efcd2040f78db8052dc2e09e06f1dfe4
Reviewed-on: https://review.typo3.org/53023


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benjamin Kott <benjamin.kott@outlook.com>
Tested-by: Benjamin Kott <benjamin.kott@outlook.com>
Reviewed-by: Markus Sommer <markussom@posteo.de>
Tested-by: Markus Sommer <markussom@posteo.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>