[BUGFIX] Properly add crop variants parameter to preview url

Using the hook
['Backend/Form/Element/ImageManipulationElement']['previewUrl'],
one can define a preview url for the image
manipulation wizard. If defined, a button
is displayed, opening the defined url in a
new window, while adding the crop variants
as an additional query parameter.

However, the query parameter was previously
always added using "&" which failed, in case
the defined preview url does not already define
query parameters.

This is now fixed by properly checking whether
the url already contains further parameters when
adding the crop variants.

Resolves: #97236
Releases: main, 11.5
Change-Id: Iedfdfa10db036490a4a801b1614ad99016f0bdc3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74029


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>