In `bp_get_the_profile_field_ids()` make sure field group has fields before attempting to pluck ID's from it. Fixes strict-mode debug-notice when trying to get all field ID's, typically for saving fields in bulk.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8963 cdf35c40-ae34-48e0-9cc9-0c9da1808c22