If I understand it ok,
wouldn't it be better 
`(if (and (fboundp 'imagemagick-types) erc-image-inline-rescale-to-window)` ?

If so, if you're fine with changing it, could you merge master in before? (now it's unmergeable automatically).  I can do it myself, but want to make sure I understood the point.

Thanks a lot for contributing :)