Assumes index of first value is always [0]

This breaks some fields like Content Taxonomy, whose first field value's index is the tid of the term.

wf_required_fields.inc checks values like this under wf_required_fields_get_missing_fields():

$value = $field[0][$column];

My suggestion is replace it with this code:

        $first_field_element = array_shift($field);
        $value = $first_field_element[$column];