I understand that this it is irrelevant if you have a break applied or not. You want to suppress a row if the measure is null right? Change your measure format such that NULL values are displayed as 0 or some number which you are sure will not come up as your measure value (I have faced some strange issues when I try to create an alerter directly by checking if it if NULL or not and hence this suggestion). Create an alerter that checks if your Measure display value is 0 or not. If it is 0, change the font of the entire row to white(if your background color is white). Also change the borders such that they dont show up. You cannot suppress a row based on an alerter, you can only hide it with workarounds.