message: fix a typo that caused a wrong allocation size
  this only affect the WebGL build's readPixels.
diff: @@ -2755,7 +2755,7 @@ void OpenGLDriver::readPixels(Handle<HwRenderTarget> src,
  void* vaddr = nullptr;
  std::unique_ptr<uint8_t> clientBuffer;
  #if defined(__EMSCRIPTEN__)
  - clientBuffer.reset(new uint8_t(p.size));
  + clientBuffer.reset(new uint8_t[p.size]);
  glGetBufferSubData(GL_PIXEL_PACK_BUFFER, 0, p.size, clientBuffer.get());
  vaddr = clientBuffer.get();
  #else
  