Fix bug with null id.
Fix bug with null id.

tsl3su/WorldMap_Choropleth,maxogden/topojson,studiowangfei/topojson,whoinlee/topojson,lyhpcha/topojson,koshlan/topojson,hcxiong/topojson,ststeiger/topojson,ongerit/topojson,btahir/topojson,mbostock/topojson,youprofit/topojson,AlpinHologramm/topojson