Passing a root element to siblings raises casting error

[coryodaniel]

value nil in where cannot be cast to type :id (if you want to check for nils, use is_nil/1 instead) in query:

from n in ArborBench.Node,
where: n.id != type(^549844, :id),
where: fragment("parent_id = ?", type(^nil, :id)),
select: n

(elixir) lib/enum.ex:1623: Enum."-reduce/3-lists^foldl/2-0-"/3
(elixir) lib/enum.ex:1247: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
(elixir) lib/enum.ex:1247: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3