How to sort (Ascending and Descending) values with blanks?

[smrod_]

Hello everyone! Need a bit of help with the sorting on my app. Currently, clients are sorted based on two separate upload deadlines (Initial and Final), and not every client has an initial or final.

I'm looking to see how I can invert the sorting for ascending or descending where blanks are not prioritized over actual values. Attached are images to explain what I mean. 

*Initial Uploads are prioritized over Final

First, when they are sorted via ascending order, the values that have initial uploads are way at the bottom and we're having to scroll all the way down the blanks to see what's upcoming. 

Then when they are sorted via descending order, although the initial uploads values are at the top, they are not in order on time. Again, keep in mind that initial uploads take priority over final uploads, therefore if an initial upload is added, regardless of the final upload date, it takes precedence over the final. 

What I'm looking for is to see if I can have them in ascending order, but place the actual values at the top without having to use descending order. I'm assuming this is because of the lack of clarification of blanks, but I'm not sure where to start to add a needed function in the Show If? or Valid If? for the table to ignore blanks? Any ideas with what functions to use for these blanks?