Please describe the problem:
I'm developping nautilus-actions (http://www.grumz.net/?q=taxonomy/term/8/9), an
extension that allow user to define custom action to place in the popup menu of
nautilus. For my next release, I've added the possibility to define a custom
icon, but I have two issues :

1. If the icon doesn't exist, it display an awful file icon that appears too big
(48x48 instead of 24x24 size)
2. It seems that we can use gtk-stock icons, but some of them are not recognized
like 'gtk-edit' for example and fall back with the awful default icon. And I
can't figure out which one are ok and which one are not programatically for my
configuration dialog.

Steps to reproduce:
Currently there is no stable version of my extension available but I try to keep
the CVS version usable as far as I can. So no easy way to reproduced it without
a little developement stuff.

1. Create an item with nautilus_menu_item_new() 
2. Set its fourth parameter to a filename that doesn't exist or "gtk-edit"
3. Restart Nautilus with the extension code and open the popup menu


Actual results:
An ugly icon of 48x48 size instead of 24x24 appears and put the popup menu out
of shape.

Expected results:
At least a 24x24 size icon or nothing at all. Or a nicer default icon of 24x24 size.

Does this happen every time?
Yes

Other information: