ape demuxer: fix segfault on memory allocation failure.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
(cherry picked from commit 273aab99bf)

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

libavformat/ape.c

@@ -356,6 +356,8 @@ static int ape_read_header(AVFormatContext * s, AVFormatParameters * ap)
 
     if (ape->seektablelength > 0) {
         ape->seektable = av_malloc(ape->seektablelength);
+        if (!ape->seektable)
+            return AVERROR(ENOMEM);
         for (i = 0; i < ape->seektablelength / sizeof(uint32_t); i++)
             ape->seektable[i] = get_le32(pb);
     }