Fix C++ tests

Author: NicolasHug

src/torchcodec/decoders/_core/VideoDecoder.cpp

@@ -1188,6 +1188,10 @@ VideoDecoder::RawDecodedOutput VideoDecoder::getNextRawDecodedOutputNoDemux() {
   return rawOutput;
 }
 
+VideoDecoder::DecodedOutput VideoDecoder::getNextDecodedOutputNoDemux() {
+  auto preAllocatedOutputTensor = torch::empty({0});
+  return VideoDecoder::getNextDecodedOutputNoDemux(preAllocatedOutputTensor);
+}
 VideoDecoder::DecodedOutput VideoDecoder::getNextDecodedOutputNoDemux(
     torch::Tensor& preAllocatedOutputTensor) {
   auto rawOutput = getNextRawDecodedOutputNoDemux();

src/torchcodec/decoders/_core/VideoDecoder.h

@@ -214,6 +214,7 @@ class VideoDecoder {
   };
   // Decodes the frame where the current cursor position is. It also advances
   // the cursor to the next frame.
+  DecodedOutput getNextDecodedOutputNoDemux();
   DecodedOutput getNextDecodedOutputNoDemux(
       torch::Tensor& preAllocatedOutputTensor);
   // Decodes the first frame in any added stream that is visible at a given