Fix root account setup

Set password only when provided. In Qubes root account is locked, so no
password is provided by user...

anaconda/users.py

@@ -252,6 +252,7 @@ class Users:
     def setUserPassword(self, username, password, isCrypted, lock, algo=None):
         user = self.admin.lookupUserByName(username)
 
+        if password:
             if isCrypted:
                 self.admin.setpassUser(user, password, True)
             else: