In 80de96488a (#3397) we introduced a new
error if we detect a binding loop from the Window geomerty to its layout.
But it looks like this causes a lot of error in existing project, so
make it a warning instead.
It will continue to be an error in the live preview as this will cause a
panic otherwise.
This commit also change the text of the error to include the actual
binding loop. I hope this makes it easier for users to see the loop and
help to fix it.
