That is an AD waiting to happen if it is on a loaded chamber. Have a friend who carried like that for several years until the seat belt got him. Got lucky but had one heck of a time explaining it to his wife and the upholstery shop.
The seat belt got the grip safety, cocked the hammer, and then fired the gun? My Sig won't do chit unless the grip safety is released.
Carrying a gun with one in the chamber is more risky than not having one in the chamber, regardless of weapon type...IMO. A 1911 style gun carried "cocked and locked" is safe IF you're carrying in a holster than covers the thumb safety.
If you practice a little, you can rack the slide with your left hand (for a righty) as you draw and bring the weapon up, if you have use of your left hand. If you don't, you're probably hosed anyway.
If you stick the gun in your waistbelt sans holster, all bets are then off...