appview: middleware: render 404 page for invalid user did/handle

Signed-off-by: Seongmin Lee <[e-mail]>

appview/middleware/middleware.go

···
 			if err != nil {
 				// invalid did or handle
 				log.Println("failed to resolve did/handle:", err)
-				w.WriteHeader(http.StatusNotFound)
+				mw.pages.Error404(w)
 				return
 			}