Dec 01 2021 09:17 AM
The referenced Data Column has a Formula that will return a "" to the cell when there is no value to calculate. So the cell appears EMPTY but the chart reads as a "ZERO". This only happens when there is a FORMULA being used to generate a value.
Dec 01 2021 11:55 AM
As an alternative, make the formulas return NA() instead of "". By default, charts treat #N/A as empty: