[BUGFIX] Fix slide function of cObject

Move variable value association to correct position.

Resolves: #69941
Releases: master, 7.6
Change-Id: I8bca6203f4e994a86b11f5d3be54b83e7dfdd73c
Reviewed-on: https://review.typo3.org/47089


Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>