button.gadget , GA_Image -> some image -> then NULL -> Boom

Hello, for some reason, I have a "skinnable" BOOPSI interface, and some button.gadget in it, for which I only use images with transparency and no text.
Since I have something to "switch" the looknfeel, at the beginning when theme is not loaded yet, no GA_Image is set to the buttons instances.
I have a logic of having a NULL theme, were no images are defined at all for buttons. The thing is, until a valid GA_Image is set, the button just draws empty and looks ok. If a theme is selected, I would setAttrs(button,GA_Image, (image),TAG_END );, ... but then If I select a "null" theme again, I thought it would be ok to get back to init state with:
setAttrs(button,GA_Image, NULL,TAG_END ); ... and it's not: Boom. the app would crash in one or other funny way.

... Of course it may be "defined as invalid to just setAttrs GA_Image with NULL", but well, isn't that the initial state of any button anyway ? Looks like just an untested case.

... not a drama for my current project because I just created "default images" when switching back to null theme, but well it takes memory.