[BUGFIX] DataProviderContext uses wrong member field in setter

Resolves: #58731
Releases: 6.2
Change-Id: Ic3c5417d19b165009ae500a19b565569e2d8b2b2
Reviewed-on: https://review.typo3.org/30028
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters