I think this problem occurs when there is an issue reading in the gtk-execute image from the icon theme. For example when icon doesn't exist in the theme, an unhandled exception is thrown.
I'm not in a position to do an NMU as I don't know enough about debian packaging yet. But in case it's of any help to the package maintainer I've attached a dpatch file I created which seems to solve the problem. Thanks, John Church
30Fix_gtkiconload.dpatch
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