FIX: return an empty result if response from Amazon is missing expected attributes (#13173)

* FIX: return an empty result if response from Amazon is missing attributes

Check we have the basic attributes requires to construct a Onebox for Amazon.

This is an attempt to handle scenarios where we receive a valid 200-status response from an Amazon request that does not include the data we’re expecting.

* Update lib/onebox/engine/amazon_onebox.rb

Co-authored-by: Régis Hanol <regis@hanol.fr>

Co-authored-by: Régis Hanol <regis@hanol.fr>

lib/onebox/preview.rb

@@ -40,6 +40,11 @@ module Onebox
       engine.data
     end
 
+    def verified_data
+      return {} unless engine
+      engine.verified_data
+    end
+
     def options
       OpenStruct.new(@options)
     end