Fix crash on redeclaration check of non-sub &foo var

The redeclaration check assumes the previous thing is a Routine
and crashes when it tries to reach for $!yada that isn't present
in my &foo; Callable.

Fix by checking the symbol is a Routine before trying to check
whether it's a yada.

Bug find: https://irclog.perlgeek.de/perl6/2017-02-13#i_14093827

src/Perl6/Actions.nqp

@@ -3537,7 +3537,9 @@ class Perl6::Actions is HLL::Actions does STDActions {
                 # Always install in lexpad unless predeclared.
                 my $predeclared := $outer.symbol($name);
                 if $predeclared {
-                    unless nqp::getattr_i($predeclared<value>, $*W.find_symbol(['Routine'], :setting-only), '$!yada') {
+                    my $Routine := $*W.find_symbol(['Routine'], :setting-only);
+                    unless nqp::istype(   $predeclared<value>, $Routine)
+                        && nqp::getattr_i($predeclared<value>, $Routine, '$!yada') {
                         $*W.throw($/, ['X', 'Redeclaration'],
                                 symbol => ~$<deflongname>.ast,
                                 what   => 'routine',