In saas-14, domain selector widgets are supposed to be instanciated
with a valid domain.
The problem is that some valid domains were wrongly evaluated. Indeed,
when receiving a domain which does not begin by an operator, the
"DomainTree" widget considered there is an implicit "&" operator that
should be used. This is not enough. Indeed, when evaluating the domain
["|", A, B, C], there is also an implicit "&" despite the fact the
domain starts with an operator ("|"). Because of that, previous
implementation interpreted this domain as ["|", A, "&", B, C] while
it should have been interpreted as ["&", "|", A, B, C].
Note: in master the parsing will be improved to handle wrong domains
and be decoupled of the DomainTree widget.