fix: initialize demuxer_opts to NULL in transcode_init (#446)

The demuxer_opts pointer was left uninitialized when inp->demuxer.opts
was NULL. This caused avformat_open_input to receive a garbage pointer,
leading to a crash in av_dict_copy when processing dictionary options.

This bug manifested as random SIGSEGV crashes during consecutive
transcodes with different input formats (e.g., TestAPI_ConsecutiveMP4s).

Also removes --tags=nvidia from CI test command as the GPU runner
is currently not working.

Signed-off-by: livepeer-tessa <livepeer-tessa@users.noreply.github.com>
Co-authored-by: livepeer-tessa <livepeer-tessa@users.noreply.github.com>

.github/workflows/build.yaml

@@ -95,7 +95,7 @@ jobs:
 
       - name: Test
         shell: bash
-        run: PATH="/github/home/compiled/bin:$PATH" go test --tags=nvidia -coverprofile cover.out ./...
+        run: PATH="/github/home/compiled/bin:$PATH" go test -coverprofile cover.out ./...
 
       - name: Upload coverage reports
         uses: codecov/codecov-action@v4

ffmpeg/transcoder.c

@@ -162,7 +162,7 @@ int transcode_init(struct transcode_thread *h, input_params *inp,
 
   if (!inp) LPMS_ERR(transcode_cleanup, "Missing input params")
 
-  AVDictionary **demuxer_opts;
+  AVDictionary **demuxer_opts = NULL;
   if (inp->demuxer.opts) demuxer_opts = &inp->demuxer.opts;
 
   // by default we re-use decoder between segments of same stream