mercurial/templates/static/followlines.js

--- a/mercurial/templates/static/followlines.js	Wed Mar 28 16:28:54 2018 -0700
+++ b/mercurial/templates/static/followlines.js	Mon Apr 09 22:00:11 2018 +0800
@@ -76,7 +76,7 @@
         if ( childSupportElms.length > 0 ) {
             btnSupportElm = childSupportElms[0];
         }
-        var refNode = btnSupportElm.children[0]; // node to insert <button> before
+        var refNode = btnSupportElm.childNodes[0]; // node to insert <button> before
         btnSupportElm.insertBefore(btn, refNode);
     }