Ensure variable is defined, to avoid notices or fatals.

buddypress/groups/groups-loop.php

@@ -145,6 +145,7 @@ function ( $type ) {
 }
 
 // Exclude private groups if not current user's profile or don't have moderate access.
+$private_groups = [];
 if ( bp_is_user() ) {
  $private_groups = openlab_get_user_private_memberships( bp_displayed_user_id() );
  if ( ! bp_is_my_profile() && ! current_user_can( 'bp_moderate' ) ) {