On member's profile, make sure posting an activity updates the member's header latest activity.

in r8378, a mispunctuation: '.' instead of ',' introduced a javascript error preventing the member's latest activity to be updated.

Props hnla

Fixes #5833

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8961 cdf35c40-ae34-48e0-9cc9-0c9da1808c22