message: [LineInfo] Store empty string instead of null in default construction
diff: @@ -9,7 +9,7 @@ namespace vcpkg
  int line_number;
  const char* file_name;
  - constexpr LineInfo() : line_number(0), file_name(nullptr) {}
  + constexpr LineInfo() : line_number(0), file_name("") {}
  constexpr LineInfo(const int lineno, const char* filename) : line_number(lineno), file_name(filename) {}
  std::string to_string() const;
  