catch nil case in get_lca, fixes #502
catch nil case in get_lca, fixes #502

unipept/unipept,unipept/unipept,bmesuere/uni-test,unipept/unipept,unipept/unipept,bmesuere/uni-test,bmesuere/uni-test,bmesuere/uni-test,unipept/unipept,bmesuere/uni-test