If the big file read changes size, BigFile does not update the big file statistics

Whenever BigFile plugin reads a file, the file statistics are read to figure out the number of pages. Since the file is not locked, but rather closed immediately after reading, there is a chance that another process can change the content. BigFile does not update the file statistics. Not sure what kind of error it will through, but it is worth to recalculate file statistics each time a new page is read.