Don't pass nil email address to EmailChecker

In production we have over 12k application references with nil email
addresses.

The EmailChecker class expects an email and not a nil value. This
creates a few exceptions when a candidate inputs a reference.

This commit tries to make sure this class doesn't receive a nil parameter.

app/components/candidate_interface/application_review_and_submit_component.rb

@@ -44,7 +44,7 @@ def references_with_personal_email_addresses?
       application_form.unsubmitted? &&
         # One or more of the professional references has a personal email address
         application_form.application_references.pluck(:referee_type, :email_address).any? do |referee_type, email_address|
-          referee_type != 'character' && EmailChecker.new(email_address).personal?
+          referee_type != 'character' && email_address.present? && EmailChecker.new(email_address).personal?
         end
     end