Fetching XProfile field visibility levels should not be dependant on fetching field data.

Allow the fetching of only visibility levels without field data in `BP_XProfile_Group::get()` by moving the block outside of the `$fetch_field_data` check. Fixes #5222.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7511 cdf35c40-ae34-48e0-9cc9-0c9da1808c22