Regression on combobox in dialog between RC2 and RC3

[bisam-rd]

When upgrading from RC2 to RC3, we have a regression.
Dropdown list of combo boxes in a dialog close immediatly after beeing opened by a user.
Seems to be the same with Date picker.

[pleku]

Fixed with vaadin/flow#4269 soon to be released in RC4

[bisam-rd]

Thanks