avcodec_encode_audio(): fix invalid free

Since 2bc0de38, AVFrame needs to be initialized
before calling avcodec_get_frame_defaults().
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/utils.c

@@ -1073,7 +1073,7 @@ int attribute_align_arg avcodec_encode_audio(AVCodecContext *avctx,
                                              const short *samples)
 {
     AVPacket pkt;
-    AVFrame frame0;
+    AVFrame frame0 = { 0 };
     AVFrame *frame;
     int ret, samples_size, got_packet;