Hi, Taki1980!
I experience this problem myself at every appstart. Bad news is, I do not know how to get rid of the crash. Good news is, for now it should help to REPAIR your steam installation of ARMA3 via rightclicking on the game link in steam and choose this option in the "properties\local data" menu. I hope this will help - please let me know!
PS: I use the german version of steam. As a consequence option names can differ.