I'm replacing existing Lutron dimmers in an old house with Caseta dimmers. I discovered that the green screw on the existing dimmers isn't connected to anything. The other three wires are the same color. The wall box is metal. Should I simply cap off the green ground wire on the Caseta dimmer and otherwise install per the instructions? I would assume this would still work and would be as safe as what I have currently, but I'm no electrician. I would very much appreciate guidance.