Hi everyone. I see there are some folks still having this same error and wanted to share what I did.
I had same issue although I do see the config file mentioned by @jrockowitz in web\modules\contrib\webform\config\install
I'm not using the option "sex" in any form and it's only used, it seems, in some example forms where the "Sex" form is empty.I ended up adding the option (sex) manually at admin/structure/webform/options/manage?search=&category%20=Demographic
That solved the problem and no error seems to be logged anymore, and the options (Male, Female) now show in the Example forms.I hope this helps