Summary:
Versions of flipper from before 7th August 2018 don't return any response, so we don't store any connection_config.json file.
To keep the functionality the same as with up-to-date app versions, when this happens, store an empty config file ("{}").
Reviewed By: danielbuechele
Differential Revision: D9682885
fbshipit-source-id: fd580f6bba6b6b20135aa2c076be10e1eea0f8bc
869c785c71