Inline Form Errors links to non existing field id if field validation fails.

Problem/Motivation

A validation error is not linked correctly to the entity reference field when using field widget multiple_options_select

Steps to reproduce

1. Setup a required entity reference field with multiple_options_select as widget under a few other fields.
2. Enable inline_form_errors module
3. Trigger requirement error
4. Link to requirement error don't move the screen to the field with the problem.

Proposed resolution

Make it work with inline_form_errors, without losing the current implementation: First field is highlighted with the error, independent of the delta.

Remaining tasks

2. Review patch
3. Write test

User interface changes

Requirement error is set on the first Delta of the field, instead of the field itself.

API changes

None

Data model changes

None