Empty fields not properly handle with Lock

[paulioceano]

When Signing up and login, if you left the password field blank, doesn't tell you any error.

During Sign Up, if you type a password and then errase it, the error message shown doesn't have the same style that the "can't be blank" messages shown in other fields.

[saltukalakus]

@luisrudge if the password is entered and then cleared to blank for Log In section, widget correctly shows the Can't be blank message with the versions 11.8 and below. But any versions newer than 11.8 this message doesn't pop up and widget makes a request to the server and this returns an error.