Sum if with blank option

Hello, I'm working on a formula where I would multiply the rental rate (in the LIST tab 2023 rates) times the # of days a piece of equipment is at a certain location according to the category of the equipment. I'm getting a value error on the blank ones. I just need to complete the formula to ignore the blank cells in column M. I'm sure you gurus can help with this one.. Please?? See attached example. Thank you

I wouldn't want column M to populate a zero though. I would rather have it blank so the ones with data will stand out instead. Is there another way around that?

oh ok. Thank you. That worked. Awesome.