Keep undefined nodes out of the XML output.

[HaroldPutman]

This is useful when you are deleting nodes from the JSON and rewriting XML. While I could see a case for writing an empty node in this case (<b/>), I'm fairly certain we never want the current behavior which is <b>undefined</b>.

so if you have:

const obj = {
  house: {
    pet: [
        "cat",
       "spider",
       "dog"]
   }
};
delete obj.house.pet[1]; // get rid of spider!
var result = parser.parse(obj);

You get:

<house>
  <pet>cat</pet>
  <pet>undefined</pet>
  <pet>dog</pet>
</house>

IMO you wanted:

<house>
  <pet>cat</pet>
  <pet>dog</pet>
</house>

[HaroldPutman]

(Sorry my editor also got rid of trailing whitespace on some lines)

[coveralls]

Coverage increased (+0.005%) to 99.043% when pulling 007a3a8 on HaroldPutman:suppress-undefined into 7d0a8c5 on NaturalIntelligence:master.

[amitguptagwl]

Sorry for the late response, it's a festive season here. I will check and merge it on Monday.