Comment 6 for bug 1294741

instrumented output. with fprintf(stderr, ...) inserted at some places

a single guide was added, then deleted
i don't know why the first destroy/origin set happened, but it could be normal

after the second destroy, the given function runs again
now it's clearly visible that SP_IS_CTRLPOINT(SP_GUIDELINE(object)->origin) is the one what fails
could this be a gtk-related problem? 2.24.22 here