Allow logging failed PR attempts as 0 reps

I suggest to add a simple feature, that would be to admit failed PRs by making it possible to enter a null (0) value to the amount of rep, in the order to have an idea of what we tried last set, and so that we could be more informed about our progress.
For example I'm trying a PR at 100kg, and I'm failing but I'm still writing it down in the app, so the next time I'm very aware of what I tried and what could be an achievement after the last pec workout.

Thanks for improving the app so quick, it is legit the one I've been the most satisfied ever, even outside of the workout app area.