[minor] fixing the icons in the navbar
[minor] fixing the icons in the navbar

the top item on the navbar had no icon, and the content of the menu had
two items with the same icon

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