[Bug] Selectors.GTournamentSelectorAlternative causes a crash.

[cristianocca]

Selectors.GTournamentSelectorAlternative causes a crash.

"Gen. 0 (0.00%): Max/Min/Avg Fitness(Raw) [0.00(0.00)/0.00(0.00)/0.00(0.00)]
Traceback (most recent call last):
File "C:\Users\Cristiano\Desktop\ej1\ej1.py", line 143, in
ga.evolve(freq_stats=GENERATIONS / 10)
File "C:\Python27\lib\site-packages\pyevolve\GSimpleGA.py", line 824, in evolv
e
if self.step(): break #exit if the number of generations is equal to the max
. number of gens.
File "C:\Python27\lib\site-packages\pyevolve\GSimpleGA.py", line 630, in step
crossover_empty = self.select(popID=self.currentGeneration).crossover.isEmpt
y()
AttributeError: 'NoneType' object has no attribute 'crossover'
"