I think I see whats happening. This happened after I added some new fields to my index and started populating them with data. If I'm graphing a timeframe that includes the time before those fields were added then they are in fact null and thus the message appears. If I change the timeframe to only include the time after I started populating those new fields then the message goes away. So I'm not sure how that situation should be handled by kibana.
On a related note, I see that the type listed on the visualization page does not change even after I change the type in the visualization its self. For example if I create an area graph and then go back and change it to a line graph it still shows as being an area graph on the visualizations page. Perhaps thats why the message about null data kept displaying even after I changed the chart type?
Here's a screenshot of the graph.
Thanks for your help!
Patrick