Assertion with invalid JSON string

[Michi Henning]

The following code parses the JSON string successfully, but then asserts where indicated:

    Json::Value root;
    Json::Reader reader;
    std::string s = R"(
        "a": "b"
    )";
    if (!reader.parse(s, root))
        abort();
    std::cerr << "parse OK" << std::endl;

    auto a = root["a"]; // Asserts at json_value.cpp:1136

The output is:

parse OK
src/lib_json/json_value.cpp:1136: Json::Value& Json::Value::resolveReference(const char*, bool): Assertion `type_ == nullValue || type_ == objectValue' failed.

parse() should report that the parse failed, but doesn't.