This test case is currently causing a segfault, and it's not related to the changes I made in libxmljs-cfm. I know this because I set baseUrl to null, and tested with libxmljs-mt, and the problem still occurs.
Note that it does not occur in the original libxmljs library. This gist corresponds to GitHub issue #8 on gagern/libxmljs.
I created show-bug.js here to illustrate it.