Notice when updating permalinks if install has no pages and verbose_page_rules are used

[westi]

Reported in #wordpress by shesek:

shesek: I'm getting "Warning: array_reverse() [function.array-reverse]: The argument should be an array in .../wp-includes/rewrite.php on line 790" after upgrading to 2.9
shesek: any known solution?

In my investigation I found you needed to have no pages and have a permalink configuration which caused the generation of verbose rules.

For example /%postname%/

[westi]

(in [12520]) Check that get_page_hierarchy() returns something before trying to build the verbose page rules in WP_Rewrite::page_uri_index(). Fixes #11578.

[ryan]

See also #11661