Final Cut Pro can't be opened

I downloaded a plugin for FCPX (Lut Loader via Pixel Film Studios) and installed just as directions said. After installation, I went to open Final Cut Pro and I got the error message pictured below.

After seeing this, I deleted the plugin and restarted my computer, but I am still getting this every time I try to open Final Cut Pro.

Is there any way I can fix this without deleting and reinstalling?

I have a few big projects I was in the middle of and don't want to loose them.