lavc/vvc: Add check to num_multi_layer_olss

Check that vps_each_layer_is_an_ols_flag, which indicates that "at
least one OLS specified by the VPS contains more than one layer," is
set if num_multi_layer_olss is non-zero.

Fixes: 65160/clusterfuzz-testcase-minimized-ffmpeg_BSF_VVC_METADATA_fuzzer-4665241535119360

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Frank Plowman <post@frankplowman.com>
Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit 36a986d9a1)

libavcodec/cbs_h266_syntax_template.c

@@ -911,6 +911,8 @@ static int FUNC(vps) (CodedBitstreamContext *ctx, RWContext *rw,
                 num_multi_layer_olss++;
             }
         }
+        if (!current->vps_each_layer_is_an_ols_flag && num_multi_layer_olss == 0)
+            return AVERROR_INVALIDDATA;
     }
 
     for (i = 0; i <= current->vps_num_ptls_minus1; i++) {