Ignore empty field values

Say you combined 5 fields, and for a given row only the 2nd and 3rd field have a value,
views_fields_combine_handler_field_combine::render() would generate $output something like:

array(
  0 => NULL,
  1 => 'sausage',
  2 => 'lemon',
  3 => NULL,
  4 => NULL,
);

With a separator of ", " this would return something like:
, sausage, lemon, ,

It would be a lot nicer if this displayed as:
sausage, lemon

This can be achieved by ignoring the empty values, something like this:
views_fields_combine_handler_field_combine.inc

  function render($values) {
    ...
-   return implode($separator, $output);
+   return implode($separator, array_filter($output));
  }

Needs work as a patch of the above needs to be rolled.