Fixes for JVM backend
Fixes for JVM backend

Deep recursion in `has_fallback` and the usual suspect: null.

labster/rakudo,tbrowder/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,salortiz/rakudo,labster/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,MasterDuke17/rakudo,rakudo/rakudo,rakudo/rakudo,tbrowder/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,labster/rakudo,rakudo/rakudo