[TASK] Add htmlspecial to ShowPic file properties

Follow-up to 2a85eeb6d623e74955703b254e24b958790c9a45

Resolves: #56723
Releases: 6.2
Change-Id: Ib3881b7be6f3cf87c0bc36a8a32fedcf2fa53029
Reviewed-on: https://review.typo3.org/28436
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny