how to detect empty wav files
If the files have no content then it's enough to key on size. A totally "empty" WAV file will have just a header and will almost certainly be less than 200 bytes. So it's probably enough to delete any files smaller than that. I would sort the folder by increasing size. You will probably see a sharp change from very low values to a series of much larger files. Bulk delete above that point (shift-select, delete).

If the files have some length but contain only silence, you need a more rigorous test. But from your question it doesn't sound like that's the case.