toaster.bbclass: fix crash on buildstats collection
Toaster needs buildstats to be enabled in order to
collect task statistics. The toaster.bbclass didn't
have a guard to stop task data collection if the buildstats
weren't enabled, leading to a crash.
This patch verifies that the task variables are defined before
trying to use them.
Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
