message: [terminal] Cell: Fixes image not being erased when text is written into the cell.
  This is how xterm behaves at least. Let's see how we're dealing with
  this semantic once we resume work on Good Image Protocol. ;-)
diff: @@ -225,7 +225,10 @@ inline void Cell::write(GraphicsAttributes const& _attributes, char32_t _ch, uin
  codepoint_ = _ch;
  if (extra_)
  + {
  extra_->codepoints.clear();
  + extra_->imageFragment = {};
  + }
  foregroundColor_ = _attributes.foregroundColor;
  backgroundColor_ = _attributes.backgroundColor;
  @@ -246,7 +249,10 @@ inline void Cell::write(GraphicsAttributes const& _attributes,
  codepoint_ = _ch;
  if (extra_)
  + {
  extra_->codepoints.clear();
  + extra_->imageFragment = {};
  + }
  foregroundColor_ = _attributes.foregroundColor;
  backgroundColor_ = _attributes.backgroundColor;
  @@ -310,7 +316,10 @@ inline void Cell::setCharacter(char32_t _codepoint) noexcept
  {
  codepoint_ = _codepoint;
  if (extra_)
  + {
  extra_->codepoints.clear();
  + extra_->imageFragment = {};
  + }
  if (_codepoint)
  setWidth(static_cast<uint8_t>(std::max(unicode::width(_codepoint), 1)));
  else
  