Create a bag not extended but ask to fetch causes error.

[whikloj]

Current logic in the bagit.php constructor means you can create a bag that is not extended but also make it fetch the contents of the fetch file.

To replicate, do

$tmp = "someNewDirectory";
new BagIt($tmp, false, false, true);

This results in the error Error: Call to a member function download() on null

Fetch should only be called if there is a fetch file loaded.

[whikloj]

Won't fix.