I am on Mac, yes, sorry I forgot to mention that. For me the problem is happening whenever a donecanvasdialog message is sent to a canvas, so I'd imagine that is triggering the same thing as the properties menu would? Also, if the donecanvasdialog message happens in an abstraction, it puts whatever patch the abstraction was created in into edit mode, and this seems to be where it's going into edit mode sort of silently, as in, it doesn't say [edit] at the top of the screen and there's no checkmark next to edit mode in the edit menu, but if you try to click anywhere inside the patch its obviously in edit mode as you are able to select/resize/etc. items in the patch but aren't able to click on a bang, for example, or anything else--but I've only been able to reliably reproduce this when first opening a patch that sends a donecanvasdialog message upon opening. It's happened occasionally after the patch has been opened, but usually the top of the pd window will indicate [edit] at least when a donecanvasdialog message is sent. The crash upon closing the patch happens every time, though. I realize that the donecanvasdialog thing is an unsupported method or whatever, but it seems like the crashing might be part of a more general problem somewhere, maybe?
I've just tested 0.49-0test2-i386 just now and the crash and everything preceding it is still happening. I've attached a patch demonstrating how the problem is being triggered for me, if maybe someone with a mac wants to check it out to confirm. It should open in edit mode without the [edit] message appearing in the title bar or whatever its called or the edit mode option in the edit dropdown menu being checked, and then make the patch go into edit mode again each time the donecanvasdialog message is sent, and finally it should crash pd when the window is closed.
ps - I seem to have mostly gotten around the issue by using coords instead of donecanvasdialog, which I normally do anyway, however it seems the crash is happening regardless, but I'm not completely sure that I didn't miss anything so please take that as a very tentative statement. It might just be too early yet for my brain to have come online.