This is a known issue,
There is a button as "Always refresh" on the Mobile Time Tracker application which is available under the Settings Tab.
If the "Always refresh" button is enabled and you try to Check-In/Out for Job or Travel or if you try to reload the Check-In/Out screen when there is no data connectivity on your phone, you see an error message as "L1_id"undefined". So please disable the "Always refresh" button if you are offline.
We will make necessary changes in the app such that the "Always refresh" button is automatically disabled when there is no data connectivity in our future releases.