[BUGFIX] Remove leading \ from primitive types

Change-Id: Ia24eefb1adf0c113ed033fcfe6e52c1e100e65c1
Resolves: #53859
Reviewed-on: https://review.typo3.org/25635
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler
Reviewed-by: Nico de Haen
Tested-by: Nico de Haen