Date tab does not switch to time tab when model is not set

[Narmer23]

When using the mode="datetime" and the v-model is null, when selecting a date in the date tab the modal closes and doesn't allow to select a time. If the v-model exists the behaviour is as expected.

You can check this on the demo page clearing the value of any datetime datepicker and trying to set a date with time.

This is the correct behaviour:

--
This is the wrong one (note the null model):

The gifs were made on the demo page using Chrome Version 77.0.3865.90

[TobyMosque]

I really don't know what is happening.:
the QPopupProxy didn't had a value, so i need to call the show and hide methods manually.
but in the above example, the QPopupProxy gets closed even without call the hide method.

PopupStrangeBehavior.mp4

[Narmer23]

Mmmh, it really is weird... Maybe someone at Quasar can understand what's happening?