smacker demuxer: handle possible av_realloc() failure.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
(cherry picked from commit 47a8589f7b)

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/smacker.c

@@ -286,11 +286,16 @@ static int smacker_read_packet(AVFormatContext *s, AVPacket *pkt)
         for(i = 0; i < 7; i++) {
             if(flags & 1) {
                 int size;
+                uint8_t *tmpbuf;
+
                 size = avio_rl32(s->pb) - 4;
                 frame_size -= size;
                 frame_size -= 4;
                 smk->curstream++;
-                smk->bufs[smk->curstream] = av_realloc(smk->bufs[smk->curstream], size);
+                tmpbuf = av_realloc(smk->bufs[smk->curstream], size);
+                if (!tmpbuf)
+                    return AVERROR(ENOMEM);
+                smk->bufs[smk->curstream] = tmpbuf;
                 smk->buf_sizes[smk->curstream] = size;
                 ret = avio_read(s->pb, smk->bufs[smk->curstream], size);
                 if(ret != size)