avcodec/vp3: Check for end of input in vp4_unpack_vlcs()

Fixes: Timeout (too long -> 1sec)
Fixes: 15232/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP3_fuzzer-5769583086010368

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/vp3.c

@@ -1403,6 +1403,8 @@ static int vp4_unpack_vlcs(Vp3DecodeContext *s, GetBitContext *gb,
     int eob_run;
 
     while (!eob_tracker[coeff_i]) {
+        if (get_bits_left(gb) < 1)
+            return AVERROR_INVALIDDATA;
 
         token = get_vlc2(gb, vlc_tables[coeff_i]->table, 11, 3);