QueueFile hangs on a 'corrupt' file

[pforhan]

Still researching how we got here, but we have a file filled with zeros, even the header. This causes QueueFile.expandIfNecessary to never complete, it's basically adding the fileLength each time through.

I propose we add an additional check on fileLength when we read it in readHeader. If zero (and less than zero? java ints are signed, after all) it would throw an IOException, failing fast.

[pforhan]

Update: may be related to #39