R1 on 3rd base, R2 on 1st base with 1 out. B4 hits a sharp ground ball to F6. R1 is advancing to the plate and R2 is advancing to 2nd base. R2 is obstructed by F3 while moving to 2nd base. F6 fields the batted ball and throws to F4 for a force out at 2nd base. F4 in an attempt to double B4 at 1st base throws the ball into dead ball territory. What does the umpire do in this situation?