avcodec/qdmc: Check input space in qdmc_get_vlc()

Fixes: Timeout (125sec -> 0.4sec)
Fixes: 18059/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_QDMC_fuzzer-5656195825664000

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegReviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/qdmc.c

@@ -367,6 +367,8 @@ static int qdmc_get_vlc(GetBitContext *gb, VLC *table, int flag)
 {
     int v;
 
+    if (get_bits_left(gb) < 1)
+        return AVERROR_INVALIDDATA;
     v = get_vlc2(gb, table->table, table->bits, 1);
     if (v < 0)
         return AVERROR_INVALIDDATA;