JMP 17.2.0

I came across this thread, which was a perfect solution to calculating a time difference between rows, using the formula below in a Formula Column.

`Col Cumulative Sum(Dif(:Time))`

However, I am getting a blank/missing item in the first cell of the Formula Column, which then causes my resulting graph to not start at zero.

Right now, I'm getting around it by inserting a row at the top of the data table with the same time, which results in Row 2 providing a zero-point.

Is there a way to treat the missing value as zero in a locked column? Or better yet, is there an edit I can make to the formula to form a T0 point?

Thanks in advance!