[TYPO3] Errors in "Indexing" on 4.0

[Claudio]

Hi all,
on my just upgraded site (3.8.1->4.0) I get a long list of errors when 
I enter the Tools -> Indexing -> "List Typo3 pages"  page:

Warning: reset(): Passed variable is not an array or object in
/_web/www/vhosts/typo3_src-4.0/typo3/sysext/indexed_search/mod/index.php
on line 433

Warning: Variable passed to each() is not an array or object in 
/_web/www/vhosts/typo3_src-4.0/typo3/sysext/indexed_search/mod/index.php
on line 435

The above is repeated many times before showing the list of pages.
Any hints?

Claudio