Fix IndexError in the genetic_algorithm.py when creating a new generation

[gnypit]

While debugging labyrinth_test.py, in the create_new_generation method in the Population class there is a problem with the following loop:

"""Secondly, we create the new generation with children being a result od selection and crossover operators
        on the current population:"""
        new_generation = Generation(size=self.no_parents_pairs * 2, fitness_function=self.fit_fun)

        for pair in self.current_children[0].get('children'):
            new_generation.add_member(genome=pair[0])
            new_generation.add_member(genome=pair[1])

Error traceback:

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm 2023.2.4\plugins\python\helpers\pydev\pydevd.py", line 1535, in _exec
    pydev_imports.execfile(file, globals, locals)  # execute the script
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\JetBrains\PyCharm 2023.2.4\plugins\python\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "C:\Users\jg\PycharmProjects\pyqkd\genal\labyrinth_test.py", line 370, in <module>
    main_pyqkd()
  File "C:\Users\jg\PycharmProjects\pyqkd\genal\labyrinth_test.py", line 366, in main_pyqkd
    test.run()
  File "C:\Users\jg\PycharmProjects\pyqkd\genal\genetic_algorithm.py", line 317, in run
    self.create_new_generation()
  File "C:\Users\jg\PycharmProjects\pyqkd\genal\genetic_algorithm.py", line 263, in create_new_generation
    for pair in self.current_children[0].get('children'):
                ~~~~~~~~~~~~~~~~~~~~~^^^
IndexError: list index out of range

Fix it.

[gnypit]

The current_parents list was empty, and so the children_candidates list and current_children dict were too.