List items from SharePoint list are empty -> error

Question

I have a beginner question. I am using an ajax call to get elements of a sharepoint list choice(checkboxes) column called "Orbit" to create a google pie chart:

data.d.results.forEach(function(row) {
    // each row
    row.Orbit.results.forEach(function(choiceOrbit) {
        // each choice of Orbit of single row
        if (countOrbit.hasOwnProperty(choiceOrbit)) {
            countOrbit[choiceOrbit] += 1;
        } else {
            countOrbit[choiceOrbit] = 1;
        }
    });

But if the item EDIT: (if the row is empty) i get an error:

Uncaught TypeError: Cannot read property 'results' of null
at Statistics.aspx:658
at Array.forEach (<anonymous>)
at Object.success (Statistics.aspx:632)
at i (jquery.min.js:2)
at Object.fireWith [as resolveWith] (jquery.min.js:2)
at A (jquery.min.js:4)
at XMLHttpRequest.<anonymous> (jquery.min.js:4)

How can i add an if(), so that an empty item will be neglected in the counting? Something like:

if(row.Wavebands.results.forEach!=null) 

doesnt work

Answer 1

I think the correct answer is:

data.d.results.forEach(function(row) {
  // each row
  if (row.hasOwnProperty('Orbit') && row.Orbit != null) {
    row.Orbit.results.forEach(function(choiceOrbit) {
      // each choice of Orbit of single row
      if (countOrbit.hasOwnProperty(choiceOrbit)) {
          countOrbit[choiceOrbit] += 1;
      } else {
          countOrbit[choiceOrbit] = 1;
      }
    });
  }
});

Answer 2

Try to check the length of the data.result

 if(data.d.results.length > 0)
  {
    // Add your code

  }