Instanced scene won't show in editor
Hiya I'm currently following this: http://kidscancode.org/blog/2018/04/godot3_tanks_part4/ 
Everything going well so far and I have the all the code done from part4 but the instanced bullet scene isn't showing when running the game. The code runs through it, since I put some debug messages and the position and direction are showed correctly.
```nim
    proc onTankShoot*(bullet: Variant,
                      position: Variant,
                      direction: Variant) {.gdExport.} =
        
        var b = asObject[PackedScene](bullet).instance() as PlayerBullet

        var pos = position.asVector2
        var dir = direction.asVector2
        print(pos)
        print(dir)
        print("adding bullet to the mapscene")
        self.addChild(b)
       b.start(pos, dir)
```
Full project files are here: https://github.com/zetashift/toptanksnim
So everything runs fine except that no bullets are showing up at all.