fix(editor): :black/marker might be empty

src/main/frontend/handler/editor.cljs

@@ -743,7 +743,7 @@
         properties (into {} (:block/properties block))]
     (if (and
          new-marker
-         (not= new-marker (string/lower-case (:block/marker block)))
+         (not= new-marker (string/lower-case (or :block/marker block "")))
          (state/enable-timetracking?))
       (assoc properties new-marker (util/time-ms))
       properties)))