Check for encryption_key

[marcus-at-localhost]

Is it possible to add a check for $config['encryption_key'] since this seem to be mandatory for file upload.

In my case I set the via an environment variable getenv('ENCKEY') and due to server configuration the key wasn't set and I spend quite some time to try and find out why I couldn't upload assets into a custom folder as described here:

https://forum.getfuelcms.com/discussion/comment/10704/#Comment_10704