UnassignedReferenceException: The variable snaradPrefab of strelba has not been assigned.
You probably need to assign the snaradPrefab variable of the strelba script in the inspector.
UnityEngine.Object.Instantiate[T] (T original) (at <d3b66f0ad4e34a55b6ef91ab84878193>:0)
strelba.Update () (at Assets/scripts/strelba.cs:14)