[BUGFIX] Rename event variable in multi-delete handler

The patch for #98288 accidentally overwrote the variable of the event in
the event handler for deleting multiple files. The event variables in
the modal button callbacks are renamed now.

Resolves: #98709
Related: #98288
Releases: main
Change-Id: I2d61f1215cdfe156628fcca61de524c98bfb0998
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76235


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>