avcodec/cbs_h2645: Skip all 0 NAL units

Fixes: assertion failure
Fixes: 19286/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_REDUNDANT_PPS_fuzzer-5707990724509696

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/cbs_h2645.c

@@ -568,7 +568,10 @@ static int cbs_h2645_fragment_add_nals(CodedBitstreamContext *ctx,
         // Remove trailing zeroes.
         while (size > 0 && nal->data[size - 1] == 0)
             --size;
-        av_assert0(size > 0);
+        if (size == 0) {
+            av_log(ctx->log_ctx, AV_LOG_VERBOSE, "Discarding empty 0 NAL unit\n");
+            continue;
+        }
 
         ref = (nal->data == nal->raw_data) ? frag->data_ref
                                            : packet->rbsp.rbsp_buffer_ref;