sax_parse() recovers from an error if parse_error() returns true. For a handler whose parse_error() is [[noreturn]], MSVC reports that code as unreachable (C4702), which fails the /WX module build. throwing_sax now throws under a flag, as json_sax_dom_parser does. Signed-off-by: Niels Lohmann <mail@nlohmann.me>