message: [terminal] Screen_test: use at() instead of operator[]
diff: @@ -1707,9 +1707,10 @@ TEST_CASE("render into history", "[screen]")
  string renderedText;
  renderedText.resize(2 * 6);
  auto const renderer = [&](Coordinate const& pos, Cell const& cell) {
  - renderedText[(pos.row - 1) * 6 + (pos.column - 1)] = static_cast<char>(cell.codepoint(0));
  + auto const offset = (pos.row - 1) * 6 + (pos.column - 1);
  + renderedText.at(offset) = static_cast<char>(cell.codepoint(0));
  if (pos.column == 5)
  - renderedText[(pos.row - 1) * 6 + (pos.column)] = '\n';
  + renderedText.at(offset + 1) = '\n';
  };
  SECTION("main area") {
  