avformat/apvdec: Use ffio_read_size()

Fixes potential use of uninitialized data.

Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/apvdec.c

@@ -164,7 +164,7 @@ static int apv_read_header(AVFormatContext *s)
     err = ffio_ensure_seekback(s->pb, sizeof(buffer));
     if (err < 0)
         return err;
-    size = avio_read(s->pb, buffer, sizeof(buffer));
+    size = ffio_read_size(s->pb, buffer, sizeof(buffer));
     if (size < 0)
         return size;