vima: check packet size before initializing bitstream reader

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/vima.c

@@ -141,11 +141,11 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     int8_t         channel_hint[2];
     int            ret, chan, channels = 1;
 
-    init_get_bits(&gb, pkt->data, pkt->size * 8);
-
     if (pkt->size < 13)
         return AVERROR_INVALIDDATA;
 
+    init_get_bits(&gb, pkt->data, pkt->size * 8);
+
     samples = get_bits_long(&gb, 32);
     if (samples == 0xffffffff) {
         skip_bits_long(&gb, 32);