Among the businesses without attribute, how many businesses located in Gilbert?
without attribute refers to attribute_value = 'None'; in Gilbert refers to city = 'Gilbert'
SELECT COUNT(T2.business_id) FROM Business_Attributes AS T1 INNER JOIN Business AS T2 ON T1.business_id = T2.business_id WHERE T2.city = 'Gilbert' AND T1.attribute_value IN ('None', 'no', 'false')