avformat/wtvdec: Cosmetics

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/wtvdec.c

@@ -290,7 +290,7 @@ static AVIOContext * wtvfile_open2(AVFormatContext *s, const uint8_t *buf, int b
 
         buf += dir_length;
     }
-    return 0;
+    return NULL;
 }
 
 #define wtvfile_open(s, buf, buf_size, filename) \