The safest hands in the business
^This article attempts to answer that using data up to and including Bahrain 2014, and although it includes several types of "driver related" DNFs not just crashes, most of these DNFs were crashes anyway. Of drivers with 50 or more race starts the most crash prone was Ukyo Katayama with one driver-related DNF every 3.2 starts whilst the least crash prone was Juan Manuel Fangio with one driver-related DNF every 50 starts.
Bottas is the least crash prone of current drivers in that article, although the article is missing the most recent 2 years of races. I decided to check Bottas' data myself and as of Austria 2016 he now has 1 driver-related DNF every
64 starts using the same metrics used in the article. I specify the last part because the author notes in the comments he did not include incidents where the driver was still a classified finisher, meaning Bottas' late race crash at Russia 2015 wouldn't be counted. I personally think that is the wrong way to go about it but it is what it is.