message: only log "no texture bound" in debug builds
  This is way to verbose in release builds, and since it's not
  a bug issue on GLES, we silence this for now.
diff: @@ -199,7 +199,9 @@ void OpenGLProgram::updateSamplers(OpenGLDriver* gl) noexcept {
  Handle<HwTexture> th = samplers[index].t;
  if (UTILS_UNLIKELY(!th)) {
  +#ifndef NDEBUG
  slog.w << "no texture bound to unit " << +index << io::endl;
  +#endif
  continue;
  }
  