Fix #2814 - json serialization edge case (#2924)
Fix #2814 - json serialization edge case (#2924)


nekia/incubator-superset-dev,nekia/incubator-superset-dev,nekia/incubator-superset-dev,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,asdf2014/superset,massgov/incubator-superset,BRD-CD/superset,BRD-CD/superset,zhouyao1994/incubator-superset,dmigo/incubator-superset,dmigo/incubator-superset,airbnb/superset,apache/incubator-superset,mistercrunch/panoramix,zhouyao1994/incubator-superset,massgov/incubator-superset,apache/incubator-superset,airbnb/superset,nekia/incubator-superset-dev,timifasubaa/incubator-superset,airbnb/caravel,apache/incubator-superset,FrederichCheng/incubator-superset,mistercrunch/panoramix,dmigo/incubator-superset,alanmcruickshank/superset-dev,zhouyao1994/incubator-superset,airbnb/superset,asdf2014/superset,FrederichCheng/incubator-superset,apache/incubator-superset,alanmcruickshank/superset-dev,alanmcruickshank/superset-dev,massgov/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,mistercrunch/panoramix,BRD-CD/superset,apache/incubator-superset,SingTel-DataCo/incubator-superset,airbnb/caravel,timifasubaa/incubator-superset,BRD-CD/superset,FrederichCheng/incubator-superset,alanmcruickshank/superset-dev,asdf2014/superset,dmigo/incubator-superset,timifasubaa/incubator-superset,asdf2014/superset,SingTel-DataCo/incubator-superset,airbnb/caravel,massgov/incubator-superset,airbnb/caravel,FrederichCheng/incubator-superset,mistercrunch/panoramix,SingTel-DataCo/incubator-superset,SingTel-DataCo/incubator-superset