Fix `Post.query.sync_comment_count()`. (transplanted from 14240ef05ed9ea0a474c17200f38a68b5609e7e1)
Fix `Post.query.sync_comment_count()`.
(transplanted from 14240ef05ed9ea0a474c17200f38a68b5609e7e1)

mitsuhiko/zine,mitsuhiko/zine,mitsuhiko/zine