Assert triggered using --ie

[quyykk]

Using fccf on https://github.com/endless-sky/endless-sky as follows results in an assert being triggered:

$ fccf --ie 'Name' source/
/usr/include/c++/12.1.0/string_view:239: constexpr const std::basic_string_view<_CharT, _Traits>::value_type& std::basic_string_view<_CharT, _Traits>::operator[](size_type) const [with _CharT = char; _Traits = std::char_traits<char>; const_reference = const char&; size_type = long unsigned int]: Assertion '__pos < this->_M_len' failed.
[1]    49800 IOT instruction (core dumped)  fccf --ie 'Name' source/