Fix: fleeing from a removed object not handled

evolve-die-repeat/molecular/prey/state_fleeing.gd

@@ -11,12 +11,13 @@ func enter(previous_state_path: String, data := {}) -> void:
 		finished.emit(owner.fsm.States.IDLE, {})
 
 func physics_update(_delta: float) -> void:
-	if GameManager.calc_distance(owner.position, threat.position) > threshold:		
+	if not is_instance_valid(threat) or GameManager.calc_distance(owner.position, threat.position) > threshold:		
 		finished.emit(owner.fsm.States.IDLE, {}) 
 		return
 	owner.move(flee_from(threat.position))
 
 func flee_from(pos: Vector2) -> Vector3:
+	# FIXME: What is the argument "pos" and why is it unused?
 	var diff = threat.position - owner.position
 	diff = diff.normalized() * -1
 	return Vector3(diff.x, diff.y ,0)