Frontend_latest log spamming: whats up?

2018-07-13 23:41:33 ERROR (MainThread) [frontend.js.latest.201807080] https://mydomain.duckdns.org/frontend_latest/app-47a9b8a28d18c1f03ce16f220e977662.js:2:12641 TypeError: null is not an object (evaluating 't.substr')

no idea whats happening here, just see the log file writing popup every second when on certain pages (views)

anyone know whats up and how to save this?