avcodec/wmavoice: Check remaining input in parse_packet_header()

Fixes: Infinite loop
Fixes: 18914/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAVOICE_fuzzer-5731902946541568

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 19c41969b2)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/wmavoice.c

@@ -1843,6 +1843,9 @@ static int parse_packet_header(WMAVoiceContext *s)
     skip_bits(gb, 4);          // packet sequence number
     s->has_residual_lsps = get_bits1(gb);
     do {
+        if (get_bits_left(gb) < 6 + s->spillover_bitsize)
+            return AVERROR_INVALIDDATA;
+
         res = get_bits(gb, 6); // number of superframes per packet
                                // (minus first one if there is spillover)
         n_superframes += res;