[XQuery] allow E1 to be empty sequence in E1/E2

The XQuery language draft says:

"Each operation E1/E2 is evaluated as follows: Expression E1 is evaluated,
and if the result is not a sequence of nodes, a type error is
raised.[err:XP0019]"

Shouldn't E1 be allowed to be the empty sequence?  Can it be reworded "...if
the result is not a (possibly empty) sequence of nodes..."

Thanks,
Priscilla