avcodec/vble: Check av_image_get_buffer_size() for failure

Fixes: CID1461482 Improper use of negative value

Sponsored-by: Sovereign Tech Fund
Reviewed-.by: "Xiang, Haihao" <haihao.xiang@intel.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit dd5379db5d)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/vble.c

@@ -190,6 +190,9 @@ static av_cold int vble_decode_init(AVCodecContext *avctx)
     ctx->size = avpicture_get_size(avctx->pix_fmt,
                                    avctx->width, avctx->height);
 
+    if (ctx->size < 0)
+        return ctx->size;
+
     ctx->val = av_malloc_array(ctx->size, sizeof(*ctx->val));
 
     if (!ctx->val) {