Combine the `exception` and `cant_open` error messages

assets/javascripts/templates/error_tmpl.coffee

@@ -36,13 +36,11 @@ app.templates.offlineError = (reason, exception) ->
     when 'private_mode'
       """ Your browser appears to be running in private mode.<br>
           This prevents DevDocs from caching documentations for offline access."""
-    when 'exception'
+    when 'exception', 'cant_open'
       """ An error occurred when trying to open the IndexedDB database:<br>
-          <code class="_label">#{exception.name}: #{exception.message}</code> """
+          <code class="_label">#{exception.name}: #{exception.message}</code>#{"""<br>
-    when 'cant_open'
+            This could be because you're browsing in private mode or have disallowed offline storage on the domain.
-      """ An error occurred when trying to open the IndexedDB database:<br>
+          """ if reason is 'cant_open' else ''} """
-          <code class="_label">#{exception.name}: #{exception.message}</code><br>
-          This could be because you're browsing in private mode or have disallowed offline storage on the domain. """
     when 'version'
       """ The IndexedDB database was modified with a newer version of the app.<br>
           <a href="#" data-behavior="reload">Reload the page</a> to use offline mode. """