Generated Postgres Column adding together other columns that may have null values

const supplyItem = pgTable('supply_item', {
  id: bigint('id', { mode: 'number' }).primaryKey().generatedAlwaysAsIdentity(),
  name: text('name').notNull(),
  location1name: text('location1_name'),
  location1quantity: numeric('location1_quantity'),
  location2name: text('location2_name'),
  location2quantity: numeric('location2_quantity'),
  location3name: text('location3_name'),
  location3quantity: numeric('location3_quantity'),
  totalQuantity: numeric('total_quantity').generatedAlwaysAs(
    (): SQL =>
      sql`${supplyItem.location1quantity}+${supplyItem.location2quantity}+${supplyItem.location3quantity}`,
  ),
})