Make signature destructuring with a Junction an error

Instead of infinilooping.  Fixes #3027, sorry for the delay in
applying jnthn's suggested fix.

src/Perl6/bootstrap.c/BOOTSTRAP.nqp

@@ -604,7 +604,7 @@ my class Binder {
                         $error[0] := $error[0] ~ " of parameter " ~ $varname;
                     }
                 }
-                return $result;
+                return $BIND_RESULT_FAIL;
             }
         }