avcodec/avpacket/av_packet_split_side_data: ensure that side data padding is initialized

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/avpacket.c

@@ -401,7 +401,7 @@ int av_packet_split_side_data(AVPacket *pkt){
         for (i=0; ; i++){
             size= AV_RB32(p);
             av_assert0(size<=INT_MAX && p - pkt->data >= size);
-            pkt->side_data[i].data = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE);
+            pkt->side_data[i].data = av_mallocz(size + FF_INPUT_BUFFER_PADDING_SIZE);
             pkt->side_data[i].size = size;
             pkt->side_data[i].type = p[4]&127;
             if (!pkt->side_data[i].data)