avformat/mov: perform sanity checks for heif before index building

Fixes: undefined NULL pointer use
Fixes: clusterfuzz-testcase-minimized-audio_decoder_fuzzer-6363211175493632

This performs equivalent sanity checks as are done in mov_read_trak()
before mov_build_index()

Reported-by: Dale Curtis <dalecurtis@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -10332,7 +10332,8 @@ static int mov_parse_heif_items(AVFormatContext *s)
         st->codecpar->width  = item->width;
         st->codecpar->height = item->height;
 
-        if (sc->sample_count != 1 || sc->chunk_count != 1)
+        err = sanity_checks(s, sc, item->item_id);
+        if (err)
             return AVERROR_INVALIDDATA;
 
         sc->sample_sizes[0]  = item->extent_length;