Support for disabled macaroons does not work

[PirosB3]

Even though the README states

...But if you want to start lnd with wallet encryption and macaroons disabled, just add those two parameters to the command line..

I could never get lncli-web to work without macaroon support. This is because in the app/lightning.js, macaroon support is ignored (disabled) only when macaroonPath is falsy. This can never happen as of now, because if --macaroon-path CLI argument is not specified, macaroonPath variable will simply point to the default to macaroon path.

Steps to reproduce

• Have a lnd server with disabled macaroon support
• Start an instance of lncli-web

Expected behavour

Server will start correctly

Current behavour

Server will exit with error `The specified macaroon file..."