fix for tensorboard visualization slowing execution even when it is off

apparently tensorflow still collect summary data even when no summary FileWriter is defined.

architectures/tensorflow_components/architecture.py

@@ -90,6 +90,7 @@ class TensorFlowArchitecture(Architecture):
             for idx, var in enumerate(self.trainable_weights):
                 placeholder = tf.placeholder(tf.float32, shape=var.get_shape(), name=str(idx) + '_holder')
                 self.weights_placeholders.append(placeholder)
+                if self.tp.visualization.tensorboard:
                     variable_summaries(var)
 
             self.update_weights_from_list = [weights.assign(holder) for holder, weights in