Returns null string during session start

During session startup, the call to whoopsie_identifier_generate will on some devices leave both buffer and error as NULL.

In particular, running http://pastebin.ubuntu.com/7268480/ on mako (and presumably on manta) as a *session* upstart job, with the upstart script of http://pastebin.ubuntu.com/7268498/ will get a null, null for the first 10 seconds (approximately) on mako:

Rebooting (boot in dmesg -T at Thu Apr 17 14:32:36 2014, first "init:" line at Thu Apr 17 14:32:44 2014), in the upstart logs I get a series of

2014-04-17T14:32:54+0000 (null) :: <nil>

(that's also the first such line ,10s after init)
until suddenly

2014-04-17T14:32:56+0000 (null) :: <nil>
2014-04-17T14:32:56+0000 81dc12[...]cd58 :: <nil>

I don't know what's causing this, as it doesn't make sense from what I can read in the code.

--

This bug is a fork of lp:1309237 to address only the whoopsie bits, in case you're following along.

--

Evan says “if I had to guess, I'd say this is because we don't have a non-loopback mac address until that point in the boot cycle”; instrumenting whoopsie will answer this quickly.

The real issue is not returning an error when this happens.