avcodec/wmavoice: Do not use uninitialized pitch[0]

Fixes: use of uninitialized value
Fixes: 70850/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAVOICE_fuzzer-4806127362048000

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

libavcodec/wmavoice.c

@@ -1506,6 +1506,8 @@ static int synth_frame(AVCodecContext *ctx, GetBitContext *gb, int frame_idx,
     /* Parse frame type ("frame header"), see frame_descs */
     int bd_idx = s->vbm_tree[get_vlc2(gb, frame_type_vlc, 6, 3)], block_nsamples;
 
+    pitch[0] = INT_MAX;
+
     if (bd_idx < 0) {
         av_log(ctx, AV_LOG_ERROR,
                "Invalid frame type VLC code, skipping\n");
@@ -1623,6 +1625,9 @@ static int synth_frame(AVCodecContext *ctx, GetBitContext *gb, int frame_idx,
         double i_lsps[MAX_LSPS];
         float lpcs[MAX_LSPS];
 
+        if(frame_descs[bd_idx].fcb_type >= FCB_TYPE_AW_PULSES && pitch[0] == INT_MAX)
+            return AVERROR_INVALIDDATA;
+
         for (n = 0; n < s->lsps; n++) // LSF -> LSP
             i_lsps[n] = cos(0.5 * (prev_lsps[n] + lsps[n]));
         ff_acelp_lspd2lpc(i_lsps, lpcs, s->lsps >> 1);