[BUGFIX] Clean up clipboard before using it in ContextMenu

Some item providers (context menu) access
clipboard information. Since the clipboard was
previously not properly initialized, this led to
exceptions, since no longer existing elements
could falsely be retrieved.

This is now fixed by cleaning up the clipboard
before making it available for the context
menu item providers.

Resolves: #92805
Releases: master, 10.4
Change-Id: I31d4c8fa4fa89815cbc660dbc8a4af5d111e1462
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71502


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>