Allow for empty time-slot name (fallback to project name)

Whenever I'm creating time slots, I'm forced to write a name 98% of the time. I just write in the name of the project that is already associated with the time slot.

It would have been better if I could just leave it empty and it would derive the name of the time slot from the project name.

Most timeslots I use, and I would assume that other use also for working on related tasks which usually means a certain project and uh... I really don't know what else other than the project name would I be putting there.

At the moment, if I don't name it, it just cancels the creation operation.