CiviCRM user capabilities not being applied

Civicrm unusable. Error in civicrm.php. Capabilties/Roles not getting applied. Users (including administrator) cannot update or add records. Database will allow edits/updates outside of civicrm.

Error indicated on following line

if ( is_array( $wp_roles->get_role( $role )->capabilities ) &&

Complete offending function as follows:

function wp_civicrm_capability( ){
global $wp_roles;
if ( ! isset( $wp_roles ) )

{ $wp_roles = new WP_Roles(); }

//access civicrm page menu link to particular roles
$roles = array( 'super admin', 'administrator', 'editor' );

foreach( $roles as $role ){
if ( is_array( $wp_roles->get_role( $role )->capabilities ) &&
! array_key_exists( 'access_civicrm_nav_link',
$wp_roles->get_role( $role )->capabilities ) )

{ $wp_roles->add_cap( $role, 'access_civicrm_nav_link' ); }

}
}