Bug in master when refreshing constraints node (though only when collapsed and with --enable-debug)

I've found an odd bug that is only apparent in --enable-debug builds.
It's not clear that it's a PgAdmin bug. It's rather difficult to get a
useful back trace when the code that exhibits the bug is hidden behind
event loop indirection, and I'm still not very familiar with the
codebase, so I though that this might be a good candidate to isolate
using git bisect. For what it's worth, the backtrace is available from
http://pastebin.com/m4iCqYwH .

PgAdmin crashes when I refresh the "constraints" node in the object
browser that is a child of a table. Note that this only happens when
the node is collapsed.

I've reproduced this on both my laptop and desktop. Both are Fedora
machines with wx 2.8/gtk, so perhaps someone could independently
reproduce this on a somewhat different system.

I did a git checkout to a fairly old revision - from late November
last year. The problem is present way back then, which makes it not
such a good candidate for a git bisect after all.

Does anyone have any idea why I might see this problem?

--
Regards,
Peter Geoghegan