Return error codes when wrong block is requested #6
Description
We can request three different types of block.
From op-geth's perspective it could actually be only two. Either including a decryption key or not (special handling is required for the deactivation block).
If a block request is unexpected (i.e. passing a decryption key although shutter is disabled) op geth should return an error code indicating that the op-node's state is false.