[Alerting] Resolve validation bug with empty params on connector's integration test

[cnasikas]

Some connectors has an integration test where it checks if the validation success when no params are being passed.

This PR changed the validation check and added the following comment. The issue should research and investigate if it can be resolved.

// Node.js 12 oddity:
// The first time after the server is booted, the error message will be:
//
//     undefined is not iterable (cannot read property Symbol(Symbol.iterator))
//
// After this, the error will be:
//
//     Cannot destructure property 'value' of 'undefined' as it is undefined.
//
// The error seems to come from the exact same place in the code based on the
// exact same circumstances:
//
//     https://github.com/elastic/kibana/blob/b0a223ebcbac7e404e8ae6da23b2cc6a4b509ff1/packages/kbn-config-schema/src/types/literal_type.ts#L28
//
// What triggers the error is that the `handleError` function expects its 2nd
// argument to be an object containing a `valids` property of type array.
//
// In this test the object does not contain a `valids` property, so hence the
// error.
// Why the error message isn't the same in all scenarios is unknown to me and
// could be a bug in V8.

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[elasticmachine]

Pinging @elastic/security-threat-hunting (Team:Threat Hunting)

[gmmorris]

@cnasikas - is this a SN specific thing? or is this broader and applies to other Connector Types?

[cnasikas]

@gmmorris It is specific to the incident management connectors that they have the subAction parameter. I think it has to do with the @kbn/config-schema. This PR #110684 improved it and this PR #114125 will fix it by checking only the status of the response and not the message as it is not important. I am closing the issue as there is no need to investigate.