A blank box 14 implies that is is the same value as box 1 when there is a dollar amount in box 12.
Box 14 is not usually required because it has been an 1099-R industrial standard for many years that if there is only one state in box 12 & 13 then the box 1 amount does not need to be allocated between two states - the entire box 1 amount is understood to be the state distribution so box 14 is just left blank.
But recently, there are at least two states that will reject 1099-R's with a state tax and a blank box 14 so it is okay to enter the box 1 amount into box 14 to satisfy the states requirement.