Why do i get this " Attempt to invoke virtual method 'java.lang.String java.lang.Throwable.toString() "?

Hello guys, i’ve been facing this issue for a while so i searched in thunkable ,but never found any correct solution

i know some people asked this type of question and said it was related to some missing block thing.
but in my structure i have’nt missed any blocks and my main screen works fine and loads ads fine but
When i load his Webviewer tab using a Extension ( com.ghostfox.moliata.ExtendedWebViewer )
it get this error.
Need Help Please.

Image with out error (down below )

Not knowing anything about this extension, I am nevertheless weary about logic that starts by setting something’s property to itself.

ExtendedWebViewer1.WebViewer to ExtendedWebViewer1 ??

What is the initial value of ExtendedWebViewer1 ?

(And by the way, in the “when dropz_site.Back Pressed” block, you do not need an "else if ‘true’ " logic. A simple “else” would suffice. )