[NOJIRA] fix when API doesn't return an array for list methods

[rmustafin]

Intent (What)

Sometimes in response for list methods XPM doesn't return a "second-level key". For example, we expect the XML response to have structure Categories -> Category -> content but we receive just Categories.

A real life example of such response:

<Response api-method="List"><Status>OK</Status><Categories /></Response>

I assume it can happen not just with categories but other methods.

Motivation (Why)

gem fails with https://sentry.io/organizations/ignition/issues/2260233094/?project=1314270&referrer=slack

Implementation (How)

Consequence

[rudylee]

I assume it can happen not just with categories but other methods.

I guess it's better if you can confirm this since you don't have spec to check if this is true or not.

[rmustafin]

@rudylee dig method shouldn't break current logic, it will simply prevent the error if we don't receive what's expected (empty array). i can add specs to the other methods too