Directory search for non-existent user throws SQL syntax error

When using the Directory Search of WP User Manager 2.7.1 (wpum-directory-search-form) with a name not in the Users Directory, the debug log shows an SQL syntax error (excerpt below).

WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the 
right syntax to use near ') OR() OR ( mt3.meta_key = 'last_name' AND mt3.meta_value LIKE '%schneiders%' )' at line 14 
for query SELECT DISTINCT SQL_CALC_FOUND_ROWS wp_users.* FROM wp_users 
LEFT JOIN wp_usermeta ON ( wp_users.ID = wp_usermeta.user_id )  
LEFT JOIN wp_usermeta AS mt1 ON ( wp_users.ID = mt1.user_id AND mt1.meta_key = '_hide_profile_members' )  
LEFT JOIN wp_usermeta AS mt2 ON ( wp_users.ID = mt2.user_id )  
LEFT JOIN wp_usermeta AS mt3 ON ( wp_users.ID = mt3.user_id )  
LEFT JOIN wp_usermeta AS mt4 ON ( wp_users.ID = mt4.user_id ) WHERE 1=1 AND ( ( 
  ( wp_usermeta.meta_key = 'last_name' 
	AND (  (  mt1.user_id IS NULL 
		OR 	( mt2.meta_key = '_hide_profile_members' AND mt2.meta_value = '' )
	) 
	AND   ( 
	 () OR() OR ( mt3.meta_key = 'last_name' AND mt3.meta_value LIKE '%schneiders%' )

Please let me know if you need further information. Thanks!