https://bugs.winehq.org/show_bug.cgi?id=38493
--- Comment #16 from Olivier F. R. Dierick o.dierick@piezo-forte.be --- Got the same issue (unhandled page fault at 0x00000000) with steam update May 15 2015 whose changelog states that internal web browser (CEF) was updated to 41.1x. And patch from comment 7 solves the issue (no other crash like with GTA5 subprocess).
I made a duplicate bug report before testing my own patch and finding that it was in fact the same issue.