Don't add tracks to trackInfo.js when no features are present on that track
Don't add tracks to trackInfo.js when no features are present on that track

Signed-off-by: asw12 <8548b6e71dbfbb86c7587651a89bbb41317bdf26@berkeley.edu>

limeng12/jbrowse,SuLab/jbrowse,limeng12/jbrowse,limeng12/jbrowse,SuLab/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,limeng12/jbrowse,GreggHelt2/apollo-test,erasche/jbrowse,SuLab/jbrowse,Arabidopsis-Information-Portal/jbrowse,Arabidopsis-Information-Portal/jbrowse,GMOD/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,SuLab/jbrowse,GreggHelt2/apollo-test,GMOD/jbrowse,SuLab/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,erasche/jbrowse,GreggHelt2/apollo-test,GreggHelt2/apollo-test,SuLab/jbrowse,GMOD/jbrowse,erasche/jbrowse,GMOD/jbrowse,nathandunn/jbrowse,nathandunn/jbrowse,Arabidopsis-Information-Portal/jbrowse,GreggHelt2/apollo-test,igemsoftware/Shenzhen_BGIC_0101_2013,GreggHelt2/apollo-test,erasche/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,erasche/jbrowse,Arabidopsis-Information-Portal/jbrowse,erasche/jbrowse,SuLab/jbrowse,GreggHelt2/apollo-test,GMOD/jbrowse,nathandunn/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,limeng12/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,limeng12/jbrowse,nathandunn/jbrowse,nathandunn/jbrowse,Arabidopsis-Information-Portal/jbrowse,limeng12/jbrowse,erasche/jbrowse,igemsoftware/Shenzhen_BGIC_0101_2013,limeng12/jbrowse,erasche/jbrowse,Arabidopsis-Information-Portal/jbrowse,Arabidopsis-Information-Portal/jbrowse