Generally you should check the result of functions which returns a pointer like the "newFromFile" ones. That functions generally return nil if something went wrong, in that case you can find error info in the error var. And you may look for C examples. Do you have the Krause book?
And, as GTK messages tells you, you should not reuse the same error var when an error has occurred. I have to admit that I am currently not too much motivated doing the RSVG wrapper. Currently you are the only active NIm GTK3 developer, you may loose interest or have no spare time soon, so there will be no RSVG user left. But maybe I will do, I may have some free days between Christmas and new year. But of course also many other task, Araq asked me to make nimble packages for GTK3... For your bugs, maybe your wrapper is wrong, or maybe your SVG file is invalid? Can you test with another SVG file? Maybe write some C code and try to use your SVG file?
