Fix compile_in_context with an immediate block
Fix compile_in_context with an immediate block

This situation could occur in the case of a begin-time EVAL that had a
code expression that contained an immediate QAST block. This led to the
failed $_ lookup reported in #2779, meaning that compilation of that
module no longer fails. Unfortunately, that isn't enough to make it
actually work, but it's a step closer.

softmoth/rakudo,MasterDuke17/rakudo,rakudo/rakudo,labster/rakudo,rakudo/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tbrowder/rakudo,tony-o/rakudo,softmoth/rakudo,nbrown/rakudo,rakudo/rakudo,nbrown/rakudo,softmoth/rakudo,nbrown/rakudo,labster/rakudo,MasterDuke17/rakudo,salortiz/rakudo,labster/rakudo,tony-o/rakudo,MasterDuke17/rakudo,softmoth/rakudo,tbrowder/rakudo,tbrowder/rakudo,tony-o/rakudo,labster/rakudo,rakudo/rakudo,tbrowder/rakudo,nbrown/rakudo,salortiz/rakudo,tony-o/rakudo,salortiz/rakudo,tony-o/rakudo,softmoth/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tony-o/rakudo,rakudo/rakudo,tbrowder/rakudo,labster/rakudo,nbrown/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,nbrown/rakudo