Don't force in isErronous check
Don't force in isErronous check

isErroneous forced LazyRefs through the `existsPart` combinator. This
might prompt further errors or infinite recursions, so should be avoided.

Seen in the wild when trying to trace t1756.scala with -Ylog:front and typr printer on.

dotty-staging/dotty,lampepfl/dotty,lampepfl/dotty,som-snytt/dotty,som-snytt/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,som-snytt/dotty,dotty-staging/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,som-snytt/dotty,sjrd/dotty,lampepfl/dotty,som-snytt/dotty