Response passed to the onSuccess callback

When using custom controllers, the whole response might be useful in the onSuccess callback (probably the same apply to the rest of them, but I'm applying changes as I need them to make sure I don't break the code).

In my case, for example, I'm storing the images in the database, so I need the image database ID to include it as a hidden field in the creation form. To do that, I included the ID in the response and added it to the form in the onSuccess callback.

Also, I needed to make a session.uploadr access null-safe, since this map is only initialized when a path is included, which seems to be not mandatory (and make sense to not include it in some cases, as... mine :).