Remove delete activity link for user 0

[boonebgorges]

bp_activity_content_filter() in bp-activity-templatetags.php checks to see whether it should include the Delete Activity link based (among other things) on whether $bp->loggedin_user->id == $activities_template->activity->user_id. But when the activity's user_id is 0, either because of a plugin like ​http://wordpress.org/extend/plugins/buddypress-group-twitter/ or ​http://teleogistic.net/bp-include-non-member-comments or because of an error, the non-logged-in viewers of the activity stream can see the Delete button (though it doesn't work).

I've attached a patch that checks to make sure user_id != 0.

[johnjamesjacoby]

(In [2718]) Only show delete link for logged in users. Fixes #1843. props boonebgorges