adjust send submission email

app/controllers/send_submission_email_controller.rb

@@ -14,7 +14,7 @@ class SendSubmissionEmailController < ApplicationController
       template = Template.find_by!(slug: params[:template_slug])
 
       @submitter =
-        Submitter.completed.where(submission: template.submissions).find_by!(email: params[:email].to_s.downcase)
+        Submitter.completed.where(submission: template.submissions).find_by(email: params[:email].to_s.downcase)
     elsif params[:submission_slug]
       submission = Submission.find_by(slug: params[:submission_slug])
 
@@ -27,9 +27,11 @@ class SendSubmissionEmailController < ApplicationController
       @submitter = Submitter.completed.find_by!(slug: params[:submitter_slug])
     end
 
-    RateLimit.call("send-email-#{@submitter.id}", limit: 2, ttl: 5.minutes)
+    if @submitter
+      RateLimit.call("send-email-#{@submitter.id}", limit: 2, ttl: 5.minutes)
 
-    SubmitterMailer.documents_copy_email(@submitter, sig: true).deliver_later! if can_send?(@submitter)
+      SubmitterMailer.documents_copy_email(@submitter, sig: true).deliver_later! if can_send?(@submitter)
+    end
 
     respond_to do |f|
       f.html { render :success }