How to skip fields when using DIH?

[Pulkit Singhal]

The data I'm running through the DIH looks like:

<products>
  <product>
    <new>false</new>
    <active>false</active>
    <regularPrice>349.99</regularPrice>
    <salesRankShortTerm/>
  </product>
</products>

As you can see, in this particular instance of a product, there is no
value for "salesRankShortTerm" which happens to be defined in my
schema like so:
<field name="salesRankShortTerm" type="slong"  indexed="true"  stored="true" />

Having an empty value in the incoming DIH data leads to an exception:
Caused by: java.lang.NumberFormatException: For input string: ""

1) How can I skip this field if its empty?

If I use script transformer like so:
  <script>
        <![CDATA[
        function skipRow(row) {
            var salesRankShortTerm = row.get( 'salesRankShortTerm' );
            if ( salesRankShortTerm == null || salesRankShortTerm == '' ) {
                row.put( '$skipRow', 'true' );
            }
            return row;
        }
        ]]>
  </script>
THEN, I will end up skipping the entire document :(

2) So please help me understand how I can configure it to only skip a
field and not the document?

Thanks,
- Pulkit