One does not need to have a password, perhaps even a special user account on the host to login using the remote desktop in Windows. This information was never found by me.
Either using the security policy or regedit. As shown in link above. As for regedit,
HKEY_LOCAL_MACHINE > SYSTEM > ControlSet001/currentcontrol > Control > Lsa
Find the registry key labeled “LimitBlankPasswordUse” and change the value from 1 to 0.