message: Clarify finding first non-null field error
diff: @@ -289,8 +289,11 @@ module.exports = React.createClass({
  },
  onFormValidationChange: function(fieldErrors) {
  - // Find the first error and show that.
  - const errCode = Object.values(fieldErrors).find(value => value);
  + // `fieldErrors` is an object mapping field IDs to error codes when there is an
  + // error or `null` for no error, so the values array will be something like:
  + // `[ null, "RegistrationForm.ERR_PASSWORD_MISSING", null]`
  + // Find the first non-null error code and show that.
  + const errCode = Object.values(fieldErrors).find(value => !!value);
  if (!errCode) {
  this.setState({
  errorText: null,
  