.Unique attribute has wrong pool usage

[zimmski]

This is maybe the same problem as #42.

Number = +,10([0-9]) "\n"

Numbers = +4(Number)

Unique =  "\tChoose: " $Numbers.Unique "\n"

START = Numbers,
        "Choose 4:\n",
        +4(Unique),
        "And now choose again:\n",
        +4(Unique)

Panics because .Unique makes more choices than there are items in the token Numbers. This should not panic since each .Unique usage should have its own pool.