Don't handle promisedParams error twice

[benjie]

If promisedParams resolves to an exception then the error will be handled twice; once here:

subscriptions-transport-ws/src/server.ts

Lines 418 to 425 in 34d503a

	if (e.errors) {
	this.sendMessage(connectionContext, opId, MessageTypes.GQL_DATA, { errors: e.errors });
	} else {
	this.sendError(connectionContext, opId, { message: e.message });
	}
	// Remove the operation on the server side as it will be removed also in the client
	this.unsubscribe(connectionContext, opId);

and once here:

subscriptions-transport-ws/src/server.ts

Lines 430 to 432 in 34d503a

	// Handle initPromise rejected
	this.sendError(connectionContext, opId, { message: error.message });
	this.unsubscribe(connectionContext, opId);

this PR resolves that issue. It's a very minor fix, so shouldn't require any test changes.

TODO:

• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change

[hwillson]

Great catch, thanks @benjie!