validar relaciones correctamente

app/models/metadata_belongs_to.rb

@@ -90,7 +90,9 @@ class MetadataBelongsTo < MetadataRelatedPosts
   private
 
   def post_exists?
-    value.present? && belongs_to.nil?
+    return true if sanitize(value).blank?
+
+    sanitize(value).present? && belongs_to.present?
   end
 
   def sanitize(uuid)

app/models/metadata_has_many.rb

@@ -73,6 +73,6 @@ class MetadataHasMany < MetadataRelatedPosts
   end
 
   def posts_exist?
-    has_many.size == value.size
+    has_many.size == sanitize(value).size
   end
 end