Log why gb entries weren't loaded on a gb page.

internal/http/web_handlers.go

@@ -124,6 +124,7 @@ func (h *Handlers) Guestbook(w http.ResponseWriter, r *http.Request) {
 
 	entries, err := h.guestbookDB.Entries(page, pageSize)
 	if err != nil {
+		log.Println("failed to load gb entries:", err)
 		return
 	}