Shader Replacement Error

I was finding out how to add depth of field in Unity Free, and it is very hard. I downloaded this "Shader Replacement" in the asset store because stated that it has a simple Depth-of-Field implementation. When I imported it and opened the scene "Glowing Things", it shows an error. Here is the error:

Attempting to release RenderTexture that were not gotten as a temp buffer UnityEngine.RenderTexture:ReleaseTemporary(RenderTexture) FunkyGlowingThingsEffect:OnDisable() (at Assets/Glowing Things/FunkyGlowingThingsEffect.js:72)

Did I opened the right scene? Is this the one that can show me depth of field? If yes, how can I fix the error? Or are there other ways to add depth of field on unity free? Help please.