That bug is a constant problem. You're correct, it's a memory leak that has to do with redrawing those icons and it particularly affects games with lots of objects in a layout. Basically, the more objects you have in a layout, the faster it'll crash. Obviously, working with an event sheet is even worse because that lists all of the objects for the entire game. I can open the expression editor maybe five times in an event sheet before construct crashes. The picture editor also contributes to the memory leak, and so does editing events in the event sheet without opening expression editor (though much less). I think it's been posted to the tracker three times. I mentioned it to one of the devs and they said that section of the code was a mess.
Regardless, I think this bug is the most important one that needs to be fixed. I've had to resort to finding ways to avoid opening the expression editor - I search for some other event that has a similar condition or action, copy and paste it and edit it, but that doesn't work if I have to change what variable it affects or such. Lately I've been trying to use a blank layout and paste the few objects I need into it and code there, then copy the code back into other event sheets, but deleting objects from a layout of a game the size of the one I'm working on takes a long time. Like seriously, I might as well go watch a TV show while it's doing it.
PLEASE scirra people, please fix this bug!! Even if that section of the code is a mess, is there some way that we could just not display those icons? I know most of the commands and don't use that section to retrieve them very much at all anymore, and if I need to, I can check it in another layout.