Return 1 from get_comment_pages_count() when pagination is disabled.

props obenland.
fixes #17778.

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git-svn-id: https://core.svn.wordpress.org/trunk@25106 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid a PHP notice in wpmu_create_blog() if $meta is not passed. props duck_, jeremyfelt, SergeyBiryukov. fixes #20793.
Built from https://develop.svn.wordpress.org/trunk@25127


git-svn-id: https://core.svn.wordpress.org/trunk@25107 1a063a9b-81f0-0310-95a4-ce76da25c4cd