Do not allow empty messages

server/cache_sqlite.go

@@ -68,6 +68,9 @@ func (c *sqliteCache) Messages(topic string, since sinceTime) ([]*message, error
 		if err := rows.Scan(&id, &timestamp, &msg); err != nil {
 			return nil, err
 		}
+		if msg == "" {
+			msg = " " // Hack: never return empty messages; this should not happen
+		}
 		messages = append(messages, &message{
 			ID:      id,
 			Time:    timestamp,

server/server.go

@@ -243,6 +243,9 @@ func (s *Server) handlePublish(w http.ResponseWriter, r *http.Request, v *visito
 		return err
 	}
 	m := newDefaultMessage(t.id, string(b))
+	if m.Message == "" {
+		return errHTTPBadRequest
+	}
 	if err := t.Publish(m); err != nil {
 		return err
 	}