fix wrong calculation for billable timelog
fix nil error
Revert "fix nil error"

This reverts commit 9694518d94db28c885bceb8b816b8c2f75c62a1b.
Revert "fix wrong calculation for billable timelog"

This reverts commit a51a9f29bf0702d439818cc561836a0bad55f159.
Merge branch 'dev' into dev_mirror