Qsys component editor: No modules found when analyzing null

This is a known problem for some years now. If the file has an synthesis error, no matter how minor, you will likely get this message. It is supposed to tell you the error in some meaningful way, but this is usually what you get. The only workaround I've found for this is to create a dummy project just for the component and try to synthesize it, find and fix your errors, then go back to your real project and build the component as before.