I'm not sure if simply removing is a valid solution to the problem.  For me it seems more that `num_lines++` is wrong only if `skip_line()` has been run.  IMO to make sure that the `num_lines++` doesn't go together with `skip_line()`, we should move it inside the if-branch.

Removing `skip_lines()` will slightly change the behaviour of the library, which is probably not desired.