I don't think it's bad luck to dream about dead people, it just means that they are there somewhere in the back of your mind and your subconcious brings it to the front while you sleep.
My friend dreamt of her sister last year - (she died of cancer 2 years previously). She came to tell her that everything would be OK. She woke up and called her mother and her other sister, neither of whom were particularly interested. All the phonecalls woke up her 11 year old daughter who asked what was going on.
When she told her that she had seen her sister her daughter replied - 'so what I see her all the time, she strokes my hair and holds my hand until I go to sleep'.:eek!!!!:
Anyway, it was good luck for them, they won a court case!