Actually, I'd disagree...
The gate network has been seen to have loads of safety protocols. Although its never made clear I would imagine that the source gate will close down first, and the destination gate a few moments later, after sufficient time that anything travelling (be it matter or energy) would have time to travel. The issue of precise timing between the two ends of the gate is never made clear, since editing of the footage removes synchronisation!
The Teal'c incident in "48 Hours" was due to the source gate being destroyed mid transfer...