[BUGFIX] Do no force int cast of pageUid in f:link.action

Since #81213, the `pageUid` argument is cast to an int. If that
parameter is omitted, pageUid becomes 0. UriBuilder is able to
determine the page uid by itself, but for this, $pageUid must be
null.

Resolves: #81749
Related: #81213
Releases: master
Change-Id: I030ef28efb1a3fdd14246f84c8ce8c464ba04a4d
Reviewed-on: https://review.typo3.org/53359


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Claus Due <claus@phpmind.net>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>