Fix bug where preview_pane setting wasn't always saved into user preferences (#1490362)

CHANGELOG

@@ -21,6 +21,7 @@ CHANGELOG Roundcube Webmail
 - Fix bug where forced extwin page reload could exit from the extwin mode (#1490350)
 - Fix bug where some unrelated attachments in multipart/related message were not listed (#1490355)
 - Fix mouseup event handling when dragging a list record (#1490359)
+- Fix bug where preview_pane setting wasn't always saved into user preferences (#1490362)
 
 RELEASE 1.1.1
 -------------

program/steps/mail/show.inc

@@ -185,8 +185,12 @@ if (!empty($set_seen_flag)) {
     }
 }
 
-exit;
+// Save preview_pane preference, if not set yet (#1490362)
+if ($RCMAIL->action == 'preview' && !$RCMAIL->config->get('preview_pane')) {
+    $RCMAIL->user->save_prefs(array('preview_pane' => true));
+}
 
+exit;
 
 
 function rcmail_message_attachments($attrib)