Plotting Empty Cells

In a line chart, I’m using this formula in a range: =IF(E36="","",66+(6.23*E36)+(12.7*69)-(6.8*M36)) for a series. “Show empty cells as Gaps” is selected. The series is still plotting downward to the bottom of the chart - plotting empty cells. #N/A was substituted for the "" true value in the formula, but the line still plots to the bottom of the chart. If the formula is deleted in the next cell in the range, the series does not plot to the bottom of the chart – the desired effect. How to modify the chart or series or formula to prevent the plot to the bottom of the chart?