diff --git a/docs/assets/bootstrap.zip b/docs/assets/bootstrap.zip
index fd5b621d78..a61ae844d8 100644
Binary files a/docs/assets/bootstrap.zip and b/docs/assets/bootstrap.zip differ
diff --git a/js/bootstrap-tooltip.js b/js/bootstrap-tooltip.js
index d76e51e8c9..e7bfd09bf2 100644
--- a/js/bootstrap-tooltip.js
+++ b/js/bootstrap-tooltip.js
@@ -206,7 +206,7 @@
       title = $e.attr('data-original-title')
         || (typeof o.title == 'function' ? o.title.call($e[0]) :  o.title)
 
-      title = title.toString().replace(/(^\s*|\s*$)/, "")
+      title = (title || '').toString().replace(/(^\s*|\s*$)/, "")
 
       return title
     }