lavc/vvc: Skip enhancement layer NAL units

The native VVC decoder does not yet support quality/spatial/multiview
scalability.  Bitstreams requiring this feature could cause crashes.
Patch fixes this by skipping NAL units which are not in the base layer,
warning the user while doing so.

Signed-off-by: Frank Plowman <post@frankplowman.com>
Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit bb9e4ff355)

libavcodec/vvc/vvcdec.c

@@ -782,6 +782,12 @@ static int decode_nal_unit(VVCContext *s, VVCFrameContext *fc, const H2645NAL *n
 
     s->temporal_id = nal->temporal_id;
 
+    if (nal->nuh_layer_id > 0) {
+        avpriv_report_missing_feature(fc->log_ctx,
+                "Decoding of multilayer bitstreams");
+        return AVERROR_PATCHWELCOME;
+    }
+
     switch (unit->type) {
     case VVC_VPS_NUT:
     case VVC_SPS_NUT: