5467: Allow null or empty values for configuration r=matklad a=kjeremy
Allow the client to respond to `workspace/configuration` with `null` values. This is allowed per the spec if the client doesn't know about the configuration we've requested.
This also protects against `null` or `{}` during initialize. I'm not sure if we want to interpret `{}` as "don't change anything" but I think that's a reasonable approach to take.
This should help with LSP clients working out of the box.
Fixes#5464
Co-authored-by: kjeremy <kjeremy@gmail.com>
818aeb8a24