Well this is not as easy as you might think, yet far easier than you might think.
From what I can Google I could not find a “Don’t show (blank)” button which can magically sort this out for me. There are plenty of Macros.. but who wants to have that.
So here we go.. You have this.
Simply do this.
Select a cell in your Pivot table with (blank) in it
Now change it to “ “ *The reason for multiple spaces is that sometimes you have items with only 1 space and Excel will not allow you to change the label for blank cells to an existing value.
Done, this will change the label for blank cells to your new value. However this is column specific, so do it for all the columns in your Pivot table