Tree.printTranslate not robust about beast2

[rbouckaert]

Looks like e71bd43 introduced incorrect Taxlabels block where numbers are added where they should not, e.g.:

#NEXUS

Begin taxa;
        Dimensions ntax=16;
                Taxlabels
                        1 Canis_adustus_a
                        2 Canis_adustus_b
                        3 Canis_anthus_a
                        4 Canis_anthus_b
                        5 Canis_latrans_a
                        6 Canis_latrans_b
                        7 Canis_lupus_a
                        8 Canis_lupus_b
                        9 Canis_mesomelas_a
                        10 Canis_mesomelas_b
                        11 Canis_simensis_a
                        12 Canis_simensis_b
                        13 Cuon_alpinus_a
                        14 Cuon_alpinus_b
                        15 Lycaon_pictus_a
                        16 Lycaon_pictus_b
                        ;
End;
Begin trees;
        Translate
                     1 Canis_adustus_a,
                     2 Canis_adustus_b,
                     3 Canis_anthus_a,
                     4 Canis_anthus_b,
                     5 Canis_latrans_a,
                     6 Canis_latrans_b,
                     7 Canis_lupus_a,
                     8 Canis_lupus_b,
                     9 Canis_mesomelas_a,
                    10 Canis_mesomelas_b,
                    11 Canis_simensis_a,
                    12 Canis_simensis_b,
                    13 Cuon_alpinus_a,
                    14 Cuon_alpinus_b,
                    15 Lycaon_pictus_a,
                    16 Lycaon_pictus_b
;
tree STATE_0 =...

should have no numbers in taxlabels block.