wrong tables on joins (again) to get the last and first posts member avatar
wrong tables on joins (again)
to get the last and first posts member avatar

Signed-off-by: Jessica González <52329a27ea5670aeec0efeeb0773bf1b4f1affa1@missallsunday.com>

StealthWombat/SMF2.1-more-forkery,StealthWombat/SMF2.1-more-forkery