why "operator[](KeyType && key)" assert(key exist)?

[7956968]

in this function:
const_reference operator[](KeyType && key) const
{
// const operator[] only works for objects
if (JSON_HEDLEY_LIKELY(is_object()))
{
auto it = m_data.m_value.object->find(std::forward(key));
JSON_ASSERT(it != m_data.m_value.object->end());
return it->second;
}

    JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
}

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why not just throw a error? so i can use "try catch" to handle all error.

[nlohmann]

operator[] is unchecked. If you want a check, use at.