avcodec/hevc_ps: Fix runtime error: index 32 out of bounds for type 'uint8_t [32]'

Fixes: 2010/clusterfuzz-testcase-minimized-6209288450080768

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 29808fff33)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/hevc_ps.c

@@ -170,6 +170,12 @@ int ff_hevc_decode_short_term_rps(GetBitContext *gb, AVCodecContext *avctx,
             }
         }
 
+        if (k >= FF_ARRAY_ELEMS(rps->used)) {
+            av_log(avctx, AV_LOG_ERROR,
+                   "Invalid num_delta_pocs: %d\n", k);
+            return AVERROR_INVALIDDATA;
+        }
+
         rps->num_delta_pocs    = k;
         rps->num_negative_pics = k0;
         // sort in increasing order (smallest first)