The unassigned task goes undone.
Why?
Because you gave them an option and when given an option people will choose to do less work.
And I bet that unassigned task was not a nice, fun, enjoyable task because if it was, it would not be unassigned.
It would be snapped up in an instant.
I bet that task will remain undone until it is assigned, because let’s face it, you have to force people to do the shitty tasks.
Thomas Duggan 