godot: Crash, if any variable have reference to delete node

Godot version: 3.0.6 - 3.1a3

OS/device including version: Windows 10 x64

Issue description: App is freez and crash, if any variable have reference to delete node.

Steps to reproduce:

var n
func _ready():
	n = Node.new()
	add_child(n)
	n.queue_free()   # crash
#	n = null  # no crash

Run project - and in editor go to remote debug and select Node with this var.