fix(dashboard): user id can be null when there is an anonymous user (#15592)
fix(dashboard): user id can be null when there is an anonymous user (#15592)


zhouyao1994/incubator-superset,apache/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,airbnb/caravel,zhouyao1994/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix,airbnb/caravel,airbnb/caravel,mistercrunch/panoramix,zhouyao1994/incubator-superset,apache/incubator-superset,airbnb/caravel,apache/incubator-superset,mistercrunch/panoramix,zhouyao1994/incubator-superset