Sum column if date is blank

MPH@PDX

I'm running into issues summing contracted fees for projects that are unscheduled. I have formulas set to sum fees per month already but unable to find a formula that works to sum fees based on no date entered. The formula outputs are in a summary being pulled from the active project sheet.

The month formula for Dec 2019:

=SUMIFS({Tracker Range 2}, {Tracker Range 1}, AND(@cell >= DATE(2019, 12, 1), @cell <= DATE(2019, 12, 31)))

How can I sum range 2 when range 1 is blank? I've tried =DATE(""), ISBLANK{Tracker Range 1}, "Cell is blank", and a few others with no luck.

L_123

=SUMIFS({Tracker Range 2}, {Tracker Range 1}, isblank(@cell