The chart series allow empty values, which means that if a data point has a null or NaN value there won't be a visual element drawn on the chart. The financial indicator (a type of chart series) support this, but because of their nature, if an ItemsSource is provided, the null values are threaded as zeroes (the number 0) during the automatic generation of data points. This is because, the data point values are calculated based on a function which includes a combination of the previous data item values. 

Add a mechanism like a method override or a property that can alter this behavior. In this case, if the data item of the generated data point contains a null value, the visual element should be dropped (missing) as in the standard chart series.