avformat/oggdec: Check for EOF after page header

Fixes: Infinite loop
Fixes: Ticket8594
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/oggdec.c

@@ -389,6 +389,9 @@ static int ogg_read_page(AVFormatContext *s, int *sid)
     avio_skip(bc, 8); /* seq, crc */
     nsegs  = avio_r8(bc);
 
+    if (avio_feof(bc))
+        return AVERROR_EOF;
+
     idx = ogg_find_stream(ogg, serial);
     if (idx < 0) {
         if (data_packets_seen(ogg))