eraseCell method
Implementation
void eraseCell(int index, CursorStyle style) {
final offset = index * _cellSize;
_data[offset + _cellForeground] = CellColor.normal;
_data[offset + _cellBackground] = style.background;
_data[offset + _cellAttributes] = 0;
_data[offset + _cellContent] = 0;
_underlineColors.remove(index);
_combiningCharacters.remove(index);
}