use asset pipeline for other image fetches

Author: drusepth

app/models/page_collections/page_collection.rb

@@ -51,7 +51,7 @@ def random_public_image
     end
 
     # If all else fails, fall back on default header
-    "card-headers/#{self.class.name.downcase.pluralize}.jpg"
+    ActionController::Base.helpers.asset_path("card-headers/#{self.class.name.downcase.pluralize}.jpg")
   end
 
   def first_public_image

app/models/page_types/content_page.rb

@@ -10,7 +10,7 @@ class ContentPage < ApplicationRecord
   self.authorizer_name = 'ContentPageAuthorizer'
 
   def random_image_including_private(format: :small)
-    ImageUpload.where(content_type: self.page_type, content_id: self.id).sample.try(:src, format) || "/assets/card-headers/#{self.page_type.downcase.pluralize}.jpg"
+    ImageUpload.where(content_type: self.page_type, content_id: self.id).sample.try(:src, format) || ActionController::Base.helpers.asset_path("card-headers/#{self.page_type.downcase.pluralize}.jpg")
   end
 
   def icon