I assume you are using Tiger, because AFAIK this problem only shows on Tiger, not Leopard. I reported this problem to the developers in May 2008. They did not respond.
The definition of the iconv function differs by OS and OS version and sometimes even depending on how you compile libiconv (e.g. if you use the +universal variant and whether you select 64-bit architectures or not).
If you make the proposed change, it will work for you, but start breaking for others. Software that uses iconv must detect the correct way to call the iconv function on the current OS. We could make a patch and apply it on platform darwin 8 only....