fix geojson addData return type, close #2105
fix geojson addData return type, close #2105

Neorth/Leaflet,akrzyzanowskino/TeamSE,rlugojr/Leaflet,davojta/Leaflet,jasonoverland/Leaflet,tsantacruz/RotationalMarker,stefanocudini/Leaflet,Neorth/Leaflet,Ubisense/Leaflet,sisou/Leaflet,iZucken/Leaflet,stefanocudini/Leaflet,sisou/Leaflet,tsantacruz/RotationalMarker,CapeSepias/Leaflet,Leaflet/Leaflet,geoloep/Leaflet,AP-whitehat/Leaflet,frogcat/Leaflet,geoloep/Leaflet,codeator/Leaflet,akrzyzanowskino/TeamSE,sisou/Leaflet,codeator/Leaflet,codeator/Leaflet,iOffice/Leaflet,rlugojr/Leaflet,brah/Leaflet,Ubisense/Leaflet,iOffice/Leaflet,jasonoverland/Leaflet,iZucken/Leaflet,msiadak/Leaflet,frogcat/Leaflet,Leaflet/Leaflet,geoloep/Leaflet,Trufi/Leaflet,davojta/Leaflet,AP-whitehat/Leaflet,Ubisense/Leaflet,Trufi/Leaflet,akrzyzanowskino/TeamSE,brah/Leaflet,rlugojr/Leaflet,scaddenp/Leaflet,iOffice/Leaflet,scaddenp/Leaflet,scaddenp/Leaflet,jasonoverland/Leaflet,stefanocudini/Leaflet,CapeSepias/Leaflet,Leaflet/Leaflet,Neorth/Leaflet,CapeSepias/Leaflet,frogcat/Leaflet,msiadak/Leaflet,Trufi/Leaflet,brah/Leaflet,AP-whitehat/Leaflet,tsantacruz/RotationalMarker,msiadak/Leaflet,davojta/Leaflet,iZucken/Leaflet