ffv1enc: check for malloc failure

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

libavcodec/ffv1enc.c

@@ -896,6 +896,8 @@ slices_ok:
 #define STATS_OUT_SIZE 1024 * 1024 * 6
     if (avctx->flags & CODEC_FLAG_PASS1) {
         avctx->stats_out = av_mallocz(STATS_OUT_SIZE);
+        if (!avctx->stats_out)
+            return AVERROR(ENOMEM);
         for (i = 0; i < s->quant_table_count; i++)
             for (j = 0; j < s->slice_count; j++) {
                 FFV1Context *sf = s->slice_context[j];