FIX: don't try to show svg's in summary email

app/helpers/user_notifications_helper.rb

@@ -93,6 +93,10 @@ module UserNotificationsHelper
     PrettyText.format_for_email(I18n.t(i18n_key)).html_safe
   end
 
+  def show_image_with_url(url)
+    !(url.nil? || url.downcase.end_with?('svg'))
+  end
+
   def email_image_url(basename)
     UrlHelper.absolute("#{Discourse.base_uri}/images/emails/#{basename}")
   end

app/views/user_notifications/digest.html.erb

@@ -134,7 +134,7 @@ body, table, td, th, h1, h2, h3 {font-family: Helvetica, Arial, sans-serif !impo
           <p style="color:#8f8f8f;line-height:1.3;margin:0 0 16px 0;padding:0;"><%= t.user.name -%></p>
         <% end %>
       </td>
-      <%- if t.image_url.present? -%>
+      <%- if show_image_with_url(t.image_url) -%>
         <td style="margin:0;padding:0 16px 8px 8px;text-align:right;" align="right">
           <img src="<%= url_for_email(t.image_url) -%>" height="64" style="margin:auto;max-height:64px;max-width:100%;outline:0;text-align:right;text-decoration:none;">
         </td>