Plotting empty/null/zero data

When providing a data set with zero values (or null, ...), the generated XML does not contain empty "set" XML element. As a consequence, these data points are not plotted. This is due to filters in fusioncharts.module, which discard any empty data which is empty or not numeric.

Ex: function _fusioncharts_data_single()

The following test should be enough as a filter, and should still allow to plot zero values:

function _fusioncharts_data_single($data, $attributes = array(), $jsid = NULL) {
    foreach ($data as $column) {
        if ($column[0] != '' && is_numeric($column[1])) {
            $clean_data[] = $column;
        }
    }
    ...

}