We have an option to validate the Attendance in Timesheet by not allowing to submit the time hours if any of the weekday is having an entry of time hours  without Attendance Entry. ​
How to Configure ?
Please refer below screenshot.
Go to Timesheet Setup (Advance Settings–>Preference–>Timesheet Setup) please refer below screenshot.
   
Please refeere below screen where without attendance entry it will not allow user to submit shows popup.

Note: This popup will be shown for a respective date for which you have entered time hours which don’t have any attendance. If user faces this scenario, he has to  leave that date time entry as empty and fill other day time hours which has attendance and can submit it