tail.lua is not erroring on an invalid checkpoint

[Kai S]

We're seeing our hindsight start up with a checkpointfile that contains an offset outside the file that it is reading.

hindsight.cp:

_G['input->analysis0'] = '5:10844552'
_G['input.maillog'] = 48641602
_G['analysis'] = '0:0'
_G['input'] = '5:10844552'
_G['input->output.heka'] = '5:10844552'
_G['analysis->output.heka'] = '0:0'

And the file on disk is 933852 bytes large.

Cheers