Test .subst() with no args does not infiniloop

Test for fix 7c3a3841eb
IRC: https://irclog.perlgeek.de/perl6-dev/2016-11-26#i_13630780

Author: zoffixznet

S05-substitution/subst.t

@@ -3,7 +3,7 @@ use lib 't/spec/packages';
 use Test;
 use Test::Util;
 
-plan 183;
+plan 184;
 
 # L<S05/Substitution/>
 
@@ -626,4 +626,7 @@ is '12'.subst(/(.)(.)/,{$()*2}),'24', '.. and do nifty things in closures';
         X::Str::Match::x, 'giving .subst-mutate invalid args throws';
 }
 
+# https://irclog.perlgeek.de/perl6-dev/2016-11-26#i_13630780
+throws-like { "".subst }, X::Multi::NoMatch, '.subst with no arguments throws';
+
 # vim: ft=perl6