Uncaught TypeError: Cannot read property 'length' of undefined

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Javascript

Hello, first of all i tried Google. But it seems I couldn't find their point. So i'm using the LinkedIn API. I have this function.

search_records: function(fn, ln) {
   IN.API.PeopleSearch()
        .fields("id", "firstName", "lastName", "headline", "industry")
        .result(function(e) {
           var results = e.people.values;
           var people = [];
           
           for (var i=0; i < results.length; i++) {
               people.push(results[i]);
           }

           . . . . . . . 

           /* I have codes that need those values */

           results[i].id;
           results[i].firstName

           etc . . .
        });
}

My problem is the subject error. How do i catch it, because sometimes that data being passed to me have less info than what i require, so i think that is the cost of the length undefined. So how to solve this?.