juju config prints empty json to stdout for invalid app names

[Mert Kirpici]

If `juju config` is called with an invalid app or config option name, it will print the an error message into stderr, alongside a valid empty json object into stdout.

miles@mertkirpici-bastion-focal:~$ juju config foo
{}
ERROR application "foo" not found (not found)

miles@mertkirpici-bastion-focal:~$ juju config keystone foo
{}
ERROR key "foo" not found in "keystone" application config or charm settings.

miles@mertkirpici-bastion-focal:~$ juju config keystone foo 2>/dev/null
{}

I am not sure if this is by design, however `list-actions` only prints error into stderr.

miles@mertkirpici-bastion-focal:~$ juju list-actions foo
ERROR application "foo" not found