Avoid crashes when a phase is missing
Avoid crashes when a phase is missing

This happens in pickler tests, where the Inlining phase does not exist.

dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty