How to Remove Empty Value Option in Multiple Select Field Using a Formula

I have a multiple Select field that takes entries from a form. Often times it comes in with one of the options being empty or null in value. See Screen shot.
I’m trying to create a formula that removes this empty Value and the “,” for it. I’ve used all of the ARRAY formulas and they aren’t working.
Multiple select Has: ,17,18,19
I want the Formula Field to be: 17,18,19 (removing the first null value and the one between 18/19)

Screen shot shows both fields and that the empty field remains.

LEFT(FieldName,LEN(FieldName)-2*(RIGHT(FieldName,2)=', '))