`set_next` doesn't work when `builtin_marks` are enabled

[mystilleef]

When builtin_marks are set, set_next doesn't work. Works fine when builtin_marks are empty.

I use Neovim HEAD.

[chentoast]

Moving to builtin marks is disabled, since there is a bad interaction with moving to and then setting the ‘ mark at the same time. However, it should be possible to allow movement to the other builtin marks. I can take a look when I have time.

[mystilleef]

Perhaps, I don't understand. I'm trying to set new marks using set_next, not move to marks. When builtin_marks are enabled, that API doesn't work.

[chentoast]

Whoops, I misread that as get_next. It should be a simple fix.