message: Fix WebGL debug build (assert with 3-channel images)
diff: @@ -94,10 +94,18 @@ Builder& Builder::miplevel(size_t level, size_t layer, const LinearImage& floatI
  std::unique_ptr<uint8_t[]> data = applyTransferFunction ?
  fromLinearTosRGB<uint8_t, 1>(sourceImage) : fromLinearToGrayscale<uint8_t>(sourceImage);
  basisImage->init(data.get(), floatImage.getWidth(), floatImage.getHeight(), 1);
  - } else {
  + } else if (sourceImage.getChannels() == 4) {
  std::unique_ptr<uint8_t[]> data = applyTransferFunction ?
  fromLinearTosRGB<uint8_t, 4>(sourceImage) : fromLinearToRGB<uint8_t, 4>(sourceImage);
  basisImage->init(data.get(), floatImage.getWidth(), floatImage.getHeight(), 4);
  + } else if (sourceImage.getChannels() == 3) {
  + std::unique_ptr<uint8_t[]> data = applyTransferFunction ?
  + fromLinearTosRGB<uint8_t, 3>(sourceImage) : fromLinearToRGB<uint8_t, 3>(sourceImage);
  + basisImage->init(data.get(), floatImage.getWidth(), floatImage.getHeight(), 3);
  + } else {
  + assert_invariant(false);
  + mImpl->error = true;
  + return *this;
  }
  return *this;
  