Fix domain composition between screen and attribute domains

domains can not be summed because they can be of 'OR' type

review985002
(transplanted from ba60f315fc3e9346c438edd10cdcc2470abd1317)

--HG--
extra : transplant_source : %BA%60%F3%15%FC%3E%93F%C48%ED%D1%0C%DC%C2G%0A%BD%13%17
Fix fallback value of get_preferences
(transplanted from b70b126c0b22c7db6ad9aeb30a752b47eaeeeba2)

--HG--
extra : transplant_source : %B7%0B%12l%0B%22%C7%DBj%D9%AE%B3%0Au%2BG%EA%EE%EB%A2