First off, the whole idea of a non-lucid dream is ALWAYS that the dreaming ego believes the dream to be reality. If it's not so, it's automatically a lucid dream.
Then, why would you die from a dream? That's pretty idiotic, you don't even move your limbs so why would you just go ahead and die? Secondly, if that was the case, why would the subconsciousness intend to commit suicide? Bullshit. Thirdly a mental adventure isn't going to kill you because it's physiologically impossible.
I died in normal dreams before and usually the dream just ended there. For example, someone shot me in the head, and I broke down and the dream just faded. And BTW I don't belive in God or the persistence of mind after death. But that doesn't even matter in a dream, does it... You don't die... and if you know that you don't die there's no reason to fear it... In a normal dream you fear it because you think you really die and the lucid death doesn't have anything to do with real life death because you obviously keep living as you are aware that it'S just a dream.
A dream death doesn't have much to do with a real life death in any way.