Garage door torsion bar support bracket not attached
Perhaps they left it unattached because there is no automatic door opener installed and they they assumed that it would be taken care of when one is installed.

It should be secured to keep the bar from flexing in the middle due to the high amount of torque in the springs. 

You can attach a piece of wood of the appropriate thickness to the header with 3" screws and secure the bracket to it with 3/8 x 2 1/2" lag bolts. 

If you are going to get a door opener in near future you could wait and see if the opener hardware will dictate the placement of it.