[BUGFIX] Group permissions for new pages are not set

This is a regression to #54085 which accidentally converted a !strcmp()
to !==.

Resolves: #56393
Releases: 6.2
Change-Id: Ie0b2e169916e6b0ea848510e615b05d68be02199
Reviewed-on: https://review.typo3.org/29875
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes
Reviewed-by: Loek Hilgersom
Tested-by: Loek Hilgersom
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters