Merge branch 'github-actions' into master

Author: ahmedfgad

pygad/pygad.py

@@ -1710,12 +1710,8 @@ def cal_pop_fitness(self):
                     # Reaching this block means that batch fitness calculation is used.
 
                     # Indices of the solutions to calculate their fitness.
-                    solutions_indices = numpy.array([
-                        sol_idx
-                        for (sol_idx, fitness)
-                        in enumerate(pop_fitness)
-                        if fitness is undefined_pop_fitness
-                    ])
+                    solutions_indices = [idx for idx, fit in enumerate(pop_fitness) if type(fit) is str and fit == "undefined"]
+
                     # Number of batches.
                     num_batches = int(numpy.ceil(len(solutions_indices) / self.fitness_batch_size))
                     # For each batch, get its indices and call the fitness function.