Fixes #223 - handle case when .graphqlconfig defines projects

[mgadda]

In addition to fix the issue details in #223, this patch also addresses the errors we were seeing in the console this morning:

(node:4595) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot convert undefined or null to object
(node:4595) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

The above unhandled error was raised by invoking Object.values(undefined) in MessageProcessor.js in the case where a .graphqlconfig file defined project-level settings.