Safari silent crash/quit with no error message
Subject mostly says it all. If I leave my Mac for an hour or more, with Safari running, when I get back most of the time Safari is no longer open, and there's no error message in Finder or (from what I can discern) in Console.
This happens on a MBPro and an iMac, and has been happening since Mavericks. Now running Yosemite. I've reported this to Apple but characteristically without a response. It's not a show-stopper, and Safari works fine when it's running, but it's becoming a tiresome problem.
iMac, OS X Yosemite (10.10.1)