How do I create a table calculation to be blank if a certain condition is met

[LucasO1]

Hi All I have a table calculation (call it Incident Rate). For 3 rows, the value is blank, and for 1 row, the value is 0.000.

This is causing my chart to look weird, see screenshot.

Is there a calculation I can use to make the null values blank so the chart starts from 0.015 (January)?