Cognos Line Chart Continue Line when there is no data

[mypriend]

Hello - does anyone know how to make a continuous line in a Cognos line chart when the data is null?  Currently, the line will break when there is no data. I can't replace the nulls with zero's because the data at that point is not zero, it just doesn't exist, so the line needs to be continuous between the points. Thanks in advanced for your help.