proper error handling in file size retrieval, patch by Ronald S. Bultje rbultje…

proper error handling in file size retrieval, patch by Ronald S. Bultje rbultje at ronald bitfreak net

Originally committed as revision 7736 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/aviobuf.c

@@ -172,7 +172,9 @@ offset_t url_fsize(ByteIOContext *s)
         return -EPIPE;
     size = s->seek(s->opaque, 0, AVSEEK_SIZE);
     if(size<0){
-        size = s->seek(s->opaque, -1, SEEK_END) + 1;
+        if ((size = s->seek(s->opaque, -1, SEEK_END)) < 0)
+            return size;
+        size++;
         s->seek(s->opaque, s->pos, SEEK_SET);
     }
     return size;