BUG #7504: corrupted statistics file "pg_stat_tmp/pgstat.stat"

The following bug has been logged on the website:

Bug reference: 7504
Logged by: shenqw
Email address: shenqw(at)163(dot)net
PostgreSQL version: 9.1.5
Operating system: FreeBSD 9.1 P4
Description:

Aug 23 11:12:11 www postgres[32088]: [2-1] WARNING: corrupted statistics
file "pg_stat_tmp/pgstat.stat"
Aug 23 11:12:11 www postgres[32088]: [3-1] WARNING: corrupted statistics
file "pg_stat_tmp/pgstat.stat"
......
Aug 24 05:51:52 www postgres[32088]: [543-1] WARNING: corrupted statistics
file "pg_stat_tmp/pgstat.stat"
Aug 24 05:51:52 www postgres[32088]: [544-1] WARNING: corrupted statistics
file "pg_stat_tmp/pgstat.stat"

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pgsql 32088 0.0 1.6 584548 33724 ?? Ss Thu10am 0:06.84
postgres: autovacuum launcher process (postgres)

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Maybe this is a bug.
if stats collector process don't product pg_stat_tmp/pgstat.stat file, the
autovacuum launcher process will output those WARNING message?