Fix token nonce to support nil billing address

lib/active_merchant/billing/gateways/braintree/token_nonce.rb

@@ -92,7 +92,7 @@ def billing_address_from_options
       def build_nonce_credit_card_request(payment_method)
         billing_address = billing_address_from_options
         key_replacements = { city: :locality, state: :region, zipCode: :postalCode }
-        billing_address.transform_keys! { |key| key_replacements[key] || key }
+        billing_address&.transform_keys! { |key| key_replacements[key] || key }
         {
           creditCard: {
             number: payment_method.number,

test/unit/gateways/braintree_token_nonce_test.rb

@@ -25,6 +25,7 @@ def setup
       ach_mandate: 'ach_mandate'
     }
     @generator = TokenNonce.new(@braintree_backend, @options)
+    @no_address_generator = TokenNonce.new(@braintree_backend, { ach_mandate: 'ach_mandate' })
   end
 
   def test_build_nonce_request_for_credit_card
@@ -66,6 +67,23 @@ def test_build_nonce_request_for_bank_account
     assert_equal bank_account_input['individualOwner']['lastName'], bank_account.last_name
   end
 
+  def test_build_nonce_request_for_credit_card_without_address
+    credit_card = credit_card('4111111111111111')
+    response = @no_address_generator.send(:build_nonce_request, credit_card)
+    parse_response = JSON.parse response
+    assert_client_sdk_metadata(parse_response)
+    assert_equal normalize_graph(parse_response['query']), normalize_graph(credit_card_query)
+    assert_includes parse_response['variables']['input'], 'creditCard'
+
+    credit_card_input = parse_response['variables']['input']['creditCard']
+
+    assert_equal credit_card_input['number'], credit_card.number
+    assert_equal credit_card_input['expirationYear'], credit_card.year.to_s
+    assert_equal credit_card_input['expirationMonth'], credit_card.month.to_s.rjust(2, '0')
+    assert_equal credit_card_input['cvv'], credit_card.verification_value
+    assert_equal credit_card_input['cardholderName'], credit_card.name
+  end
+
   def test_token_from
     credit_card = credit_card(number: 4111111111111111)
     c_token = @generator.send(:token_from, credit_card, token_credit_response)