Need a blank cell when IF cell is blank

Long time listener, first time caller...

I'm sure this is simple, but I don't know how to do it.
I am putting together a very simple spreadsheet that will autopopulate the correct shift when a manager is input into a cell. I need to do this cell by cell, because some of the managers overlap shifts.

In place of "name" and "shift" I have the actual manager and shift, but for simplicity sake I have:

=IF(K21="NAME", "SHIFT1", "SHIFT2")

and that works just fine for this because there are only 2 managers with different shifts.

However, when there are no manager names in K21, it still gives me a shift in the other cell.

How do I leave that blank until the manager name is filled in?

(I will also need to have several other "IF" statements in other cells, as there are more managers on those shifts, and nested IF statements are telling me there are too many arguments. Not sure what I'm doing wrong.)