FIX Explicitly set the PostsPerPage during migration
FIX Explicitly set the PostsPerPage during migration

Tested against the silverstripe.org codebase, BlogHolder migration fails unless you set this.
lekoala/silverstripe-blog,gordonbanderson/silverstripe-blog,kinglozzer/silverstripe-blog,camfindlay/silverstripe-blog,javabrett/silverstripe-blog,lekoala/silverstripe-blog,kinglozzer/silverstripe-blog,javabrett/silverstripe-blog,gordonbanderson/silverstripe-blog,javabrett/silverstripe-blog,lekoala/silverstripe-blog,silverstripe/silverstripe-blog,micmania1/silverstripe-blog,gordonbanderson/silverstripe-blog,camfindlay/silverstripe-blog,silverstripe/silverstripe-blog,camfindlay/silverstripe-blog,micmania1/silverstripe-blog,micmania1/silverstripe-blog