Ufo crashes since repository rakudo  2014.05-128-gf146fec 

Since this commit https://github.com/rakudo/rakudo/commit/7d6acc7a0bea2a0588e77c70648655c9e947639d ```CompUnitRepo::Local::Installation``` is not a ```Str```

I don't know whether this is temporary workaround or real fix but this change solves problem in my case.