So to clarify (because this is a historic post and the same thing happened to me today): This happens not because it’s an empty class, but because you didn’t click on “Public” or “Private” so the path on the include at the top of the CPP file doesn’t resolve properly with default settings?
I fixed mine by changing it to ‘./headerfilename.h’ because they’re in the same folder for this case. So it’ll break if I move them of course…
But effectively the build breaks because you didn’t click an optional button?