How to ignore blank cels in x axis
 

I would like to have a line chart that I change the x-axis values with an "if" statement.
Problem is number of x-axis values changes according to the selection (I want 12 periods of months or 8 Quarters according to the selection)
But I can not make my chart to ignore the last 4 blank cells automatically when I convert the the graph to Quarter view

Can anyone help?

Thanks