Post Process Material questions. Light Only

Hi guys! Im working on a Post Process to affect any model i import to the project. I’m dividing post process in put 0 by base color to extract the light of the image, like i learn in a unreal class. The problem is that object with 0,0,0 RGB are beeing excluded from the render, and the light are not affecting them anymore. I tryied to add some values to not divide by 0, but didn’t work. Using this post to another question about Post Process, how can extract metalic and roughness from the view? I was trying to work on the metal and rough mask node but its nulling the light and shadow from the objects too.