Ensure "Groups" reads groups-for-user from main site

includes/civicrm-network-groups-hooks.php

@@ -202,9 +202,21 @@ class CiviCRM_Network_Groups_Hooks {
 			return $groups;
 		}
 
-		// Get user's "Groups" groups.
+		// Maybe switch to main site.
+		$switched = false;
+		if ( is_multisite() AND ! is_main_site() ) {
+			switch_to_blog( get_main_site_id() );
+			$switched = true;
+		}
+
+		// Get user's "Groups" groups on the main site.
 		$wp_group_ids = $this->plugin->wordpress->group_ids_get_for_user( $user->ID );
 
+		// Switch back.
+		if ( $switched === true ) {
+			restore_current_blog();
+		}
+
 		// Init allowed flag.
 		$allowed = false;