Error highlighting doesn't work

[kussberg]

Describe the bug
When adding new required fields, they are not highlighted red after submission.

To Reproduce
Steps to reproduce the behavior:

1. Add field that is required.
2. Submit the empty form.
3. Basic fields are highlighted red, added field stays white.

Screenshots

Expected behavior
Additional fields will also get the error class and be highlighted as default fields on the top.
Classes in case of an error:
Currently is: class="company input pmpro_required pmpro-required"
Should be: class="input pmpro_error pmpro_required"