Dialogs: Prevent user's data loss if the dialogs were closed without submit

1. Open Sign in or Sign up dialog
2. Start enter data
3. Click somewhere beyond the dialog borders (easy to make this click by mistake)

AR:
Dialog is closed
When user opens dialog again, all fields are empty
It works according to JC-1030, so it is not a bug

ER:
Input data loss is prevented some way.

Maybe it is the dialog which cannot be closed by background click if data was entered
OR maybe the data is silently saved somewhere and when user clicks "Sign up" again the dialog fields are displayed prefilled