vBulletin 4.x dev. console error is:

Uncaught TypeError: document.getElementById(...) is null
Cas_getStats https://*.*/:515
<anonymous> https://*.*/:592
*.*:515:13
Cas_getStats https://*.*/:515
<anonymous> https://*.*/:592
line 515 is:
document.getElementById('vsatopstats_rtitle_menu') .style.display='none';

line 592 is:
Cas_getStats("hottestforums", "posters");


This apparently worked to silence the error (not to fix it, I do not know how):

Inside vBulletin AdminCP, Styles & Templates, Search in templates:

search for: document.getElementById('vsatopstats_rtitle_menu') .style.display='none';

click found template "vsa_topstats_stats"

find again and replace lines:

document.getElementById('vsatopstats_rtitle_menu') .style.display='none';
document.getElementById('vsatopstats_ltitle_menu') .style.display='none';


by:

// document.getElementById('vsatopstats_rtitle_menu') .style.display='none';
var element = document.getElementById('vsatopstats_rtitle_menu') ;
if (element) {
element.style.display = 'none';
}
// document.getElementById('vsatopstats_ltitle_menu') .style.display='none';
var element = document.getElementById('vsatopstats_ltitle_menu') ;
if (element) {
element.style.display = 'none';
}