When the data is empty the pie chart disappears and the legend is presented. Would it be possible to present an empty ring in the place where the chart is present in the case when there is no data to present the chart?
What does your data look like when you're saying there is no data? Is there a category field still, the values are just null or 0? If I have no data, nothing shows up, unless I select the option of displaying a message where the chart should be if there is no data. Let me know.
Currently in my case when there is no data the chart is not displayed as well. The question is if it would be possible to show the outline of the empty pie chart, so that the user is not confused with the disappearing chart.