Fix stubbing attributes alongside cache_markdown_field

app/models/concerns/cache_markdown_field.rb

@@ -78,7 +78,7 @@ module CacheMarkdownField
   def cached_html_up_to_date?(markdown_field)
     html_field = cached_markdown_fields.html_field(markdown_field)
 
-    cached = !cached_html_for(markdown_field).nil? && !__send__(markdown_field).nil?
+    cached = cached_html_for(markdown_field).present? && __send__(markdown_field).present?
     return false unless cached
 
     markdown_changed = attribute_changed?(markdown_field) || false