OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15896
Crash type: Bad-cast
Crash state:
Bad-cast to Sass::PreValue from Sass::Unary_Expression
Sass::SharedImpl<Sass::PreValue>::SharedImpl<Sass::Expression>
Sass::Parser::parse_ie_keyword_arg