[BUGFIX] Follow up: Remove icon doesn't work

With patch 6711c14 the function setFormValueManipulate was corrected but
if called it returns an array instead of the first form element. This
patch makes sure that the first object is always returned.

Resolves: #56221
Releases: 6.2
Change-Id: I03445afcb15d9323cd899974ac1cf378945e4ecb
Reviewed-on: https://review.typo3.org/28010
Reviewed-by: Stefan Neufeind
Reviewed-by: Markus Klein
Tested-by: Markus Klein