Nested eager loading along OptionalParent relationship crashes

[tarag]

When performing several nested eager loading of parents along the same OptionalParent relationship, it crashes in ThroughOptionalParentEagerLoader run() (fatal error: Unexpectedly found nil while unwrapping an Optional value: file fluent-kit/Sources/FluentKit/Properties/OptionalParent.swift, line 153) when reaching the last parent that has no valid parent and attempting again to eager load this non existing parent:

public final class ZoneRecord : Model, Content {
…    
    @OptionalParent(key: "parent_id")
    public var parent : ZoneRecord?
…
}

return ZoneRecord.query(on: req.db)
    .filter(\.$id == id)
    .with(\.$parent) {
        $0.with(\.$parent) {
            $0.with(\.$parent)
        }
    }
    .first()

Example:

ZoneRecord id = 1, parent_id=nil
ZoneRecord id = 2, parent_id=1
ZoneRecord id = 3, parent_id=2

If I perform the query for a ZoneRecord that has a valid parent and grand parent it works as expected (e.g. id = 3 above), but for one that has only one parent and no grand-parent it will crash (E.g id = 2 above).

Fluent-Kit: 1.0.0-rc.1.8
fluent-postgres-driver 2.0.0-rc.1