add throw declaration if no tree in data
add throw declaration if no tree in data

BioInf-Wuerzburg/AliTV,BioInf-Wuerzburg/AliTV,BioInf-Wuerzburg/AliTV,AliTVTeam/AliTV,BioInf-Wuerzburg/AliTV,AliTVTeam/AliTV,BioInf-Wuerzburg/AliTV,BioInf-Wuerzburg/AliTV