* Invalidate the pulse if it contains no recipients

Switch statement was returning `true`, resulting in falsely "valid" pulse
in the case there were no recipients but the schedule was set to month.

This commit fixes that.

* Move all conditions before the switch statement

* Enable repro for #17657

* Guard against the error that causes the white screen

* Add another repro for #17657

* Fix typo in the test name

* Fix typo in the unrelated comment