All troll alerts aside, the answer is:
If you are so stupid as to not check the chamber before you take it apart you shouldn't be handling guns in the first place.
Maybe, maybe not. Last year, a man died at a local indoor range when disassembling a Glock pistol after failing to check the chamber.
He was not "stupid." He was a father of several childeren and a friend of my wife's boss. Why he failed to properly check the firearm, we'll never know. Was he careless? Was he distracted? Did his eyesight fail him? All we know is that humans are fallible and there was a failure to follow Rules 1, 2, and 3. Perhaps he would have survived if he only broke the first 2 Rules, but there is no doubt that a failure to follow Rule 3 is what killed him. Of course, some firearm designs require that Rule 3 be broken for disassembly.
This is not to say that these designs are inherently "less-safe" than others (the last thing I would ever propose are additional politician/lawyer-mandated "safety features"). But an adherence to the 4 Rules becomes even more critical when operating them.