Javascript Error, all pages wp dashboard

This Keeps clutering my log, besides, after error some other js crushes have ocurred.
As described on the topic, the JS error pops in every page of the dashboard,

2017-03-20 15:45:40.012 edit.php:2634 Uncaught TypeError: Cannot read property 'style' of null
    at window.onload (editphp:2634)

This appears on every page so, the actual line source can be something like (users.php:1757) (themes.php:1862) (plugins.php:1857) (user-edit.php?user_id=3&wp_http_referer=%2Fwp-admin%2Fusers.php:1916) … for naming a few. The post edit is the most annoying because on my instalation I actually use some js for automating the edition, (this is a diy fix for a theme I bought earlier, maybe not the best solution, but support at the theme developers is really slow)

Fix this please.