Automated break subtraction not valid for vacation shifts

While automatically substracted breaks (e.g. 30 min after 6h) are not counted as worktime, they appear to be for vacation shifts.

Steps to reproduce

1. Set up a contract
2. Manually create a vacation type shift from 8:30 until 17:00
3. Check the vacation panel in the Report/Timesheet view → 8:30 h of vacation will be shown
4. change the shift type to normal → 8:00 will be counted in the worktime summary

Workaround for the time being: clock two separate 4h shifts with a break.