cypress-cli type for CypressRunResult::runs is incorrect (can be null/undefined)

[xdumaine]

Current behavior:

In the event that the browser fails to connect, the run promise resolves with results which has runs of null or undefined. (Which is likely a separate issue altogether. It should probably not resolve at all - it should reject).

However, the typings indicate that the type of runs is RunResult[] which doesn't match null

Desired behavior:

The type should indicate that runs can be undefined or null, or run() should not resolve on an error running the tests altogether.

Test code to reproduce

1. Clone https://github.com/xdumaine/cypress-test-tiny
2. npm i && npm test

[ddayguerrero]

👋 Hey! While there might be work in progress, I'd be interested in helping and ultimately achieving a first time contribution for Cypress.

Following the instructions within the cypress-test-tiny fork, I've been able to reproduce the error with the following environment:

Cypress:    3.8.1
Browser:    Chrome 79

As previously mentioned and from my understanding, there are currently a couple of ways of solving this:

1. Playing around with the CypressRunResult type interface to support null or undefined special types.
2. Handling the rejected state upon invoking the promise.

Option 2 sounds like the long term solution. I think changes will be around the lines of https://github.com/cypress-io/cypress/blob/develop/packages/server/lib/plugins/util.coffee#L37 however it seems like we would need to distinguish before:browser:launch and task events.

Can I help with with 2, with the short term solution 1, or with any other suggested solution?