Error with first and last tree when using `-j`

[nylander]

--jump now prints the first tree, but then doesn't jump correctly to the second (printed tree),
as well as not printing the last tree correctly. Tried both with, and without burn in.

Examples:

$ ./burntrees.pl --DEBUG -j 2 ten.t
# I want to see trees 1,200,400,600,800
# Now I get 1,100,300,500,700,900

$ ./burntrees.pl --DEBUG  -j 2 -b 5 ten.t
# I want to see trees 500,700,900
# Now I get 500,600,800,900

$ ./burntrees.pl --DEBUG -j 2 -pb 50 ten.t
# I want to see trees 500,700,900
# Now I get 500,600,800,900

In practice, this "bias" in the sampling will obviously not be too important, but from a coding perspective, it's annoying.

File ten.t looks like this:

[ID: 1982642803]
begin trees;
   translate
       1 90CF11697,
       2 93TH057,
       3 Q23,
       4 U455,
       5 NDK,
       6 BRU;
   tree rep.1 = ((6:0.100000,(2:0.100000,(3:0.100000,4:0.100000):0.100000):0.100000):0.100000,5:0.100000,1:0.100000);
   tree rep.100 = ((((6:0.026247,5:0.046559):0.106282,3:0.053458):0.035102,4:0.067694):0.019439,2:0.050718,1:0.035614);
   tree rep.200 = ((((6:0.033915,5:0.031691):0.066453,3:0.043791):0.011200,4:0.022733):0.013564,2:0.040335,1:0.027448);
   tree rep.300 = ((((6:0.032184,5:0.032908):0.071814,3:0.028073):0.008604,4:0.029629):0.027051,2:0.023140,1:0.023315);
   tree rep.400 = ((((6:0.026597,5:0.031312):0.092707,3:0.038781):0.014175,4:0.037719):0.025004,2:0.023140,1:0.030641);
   tree rep.500 = ((((6:0.026597,5:0.036760):0.075968,3:0.036606):0.009627,4:0.035667):0.021125,2:0.023140,1:0.017511);
   tree rep.600 = (2:0.019095,(((6:0.039005,5:0.036481):0.077383,3:0.042176):0.018266,4:0.035851):0.019244,1:0.023885);
   tree rep.700 = ((((6:0.029036,5:0.036760):0.072665,3:0.031682):0.010570,4:0.041057):0.026085,2:0.017982,1:0.024265);
   tree rep.800 = ((((6:0.023029,5:0.041575):0.080674,3:0.036122):0.012265,4:0.037022):0.017145,2:0.023715,1:0.020235);
   tree rep.900 = ((((6:0.023029,5:0.041575):0.080674,3:0.040920):0.005397,4:0.030083):0.018876,2:0.023595,1:0.027359);
end;