void
pop_paper (Lily_parser *parser)
{
- if (! scm_is_null (parser->lexer_->lookup_identifier ("$papers")))
+ if (scm_is_pair (parser->lexer_->lookup_identifier ("$papers")))
parser->lexer_->set_identifier (ly_symbol2scm ("$papers"),
scm_cdr (parser->lexer_->lookup_identifier ("$papers")));
}