Using something like window.onerror
is probably a better option.
[1] Debugging · thomthom/sketchup-webdialogs-the-lost-manual Wiki · GitHub
But here’s the reg key:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\SketchUp\SketchUp 2016\WebDialogs]
"ShowErrorDialogs"=dword:00000001
This is mentioned in the Release Notes, BTW.