From 767d60156b89382326ce42f3ddca0cb860d38149 Mon Sep 17 00:00:00 2001
From: Yves Senn <yves.senn@gmail.com>
Date: Mon, 27 Apr 2015 10:15:52 +0200
Subject: mailer previews for `NullMail` instances. Closes #19849.

---
 railties/lib/rails/templates/rails/mailers/email.html.erb | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'railties/lib/rails/templates')

diff --git a/railties/lib/rails/templates/rails/mailers/email.html.erb b/railties/lib/rails/templates/rails/mailers/email.html.erb
index cce818d103..afca6368d5 100644
--- a/railties/lib/rails/templates/rails/mailers/email.html.erb
+++ b/railties/lib/rails/templates/rails/mailers/email.html.erb
@@ -103,7 +103,14 @@
   </dl>
 </header>
 
-<iframe seamless name="messageBody" src="?part=<%= Rack::Utils.escape(@part.mime_type) %>"></iframe>
+<% if @part.mime_type %>
+  <iframe seamless name="messageBody" src="?part=<%= Rack::Utils.escape(@part.mime_type) %>"></iframe>
+<% else %>
+  <p>
+    You are trying to preview an email that does not have any content.
+    This is probably because the <em>mail</em> method has not been called in <em><%= @preview.preview_name %>#<%= @email_action %></em>.
+  </p>
+<% end %>
 
 </body>
 </html>
-- 
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