[BUGFIX] FollowUp to #56797 in I1f15fbd262036b6b2d0159cd0e9613ad7135a296

Somehow a double $this->$this slipped into the cleanup on line 390
which now fatals. This needs to be fixed.

Resolves: #56797
Releases: 6.2
Change-Id: Ibb23b5f56c95106c4fea6e9a3ba09fbc9f9905dd
Reviewed-on: https://review.typo3.org/28296
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny