Issue with _objective function

I noticed that there is something that seems like a bug to me with the _objective function, more specifically with calculating the logp(z|x):
`log_QzGx = (-(self.z_dim / 2) * log2pi + tf.reduce_sum(- tf.log(sigma) - 0.5 * tf.squared_difference(z, mu) / (2 * tf.square(sigma)), -1))`
In the second part you multiply with 0.5 and then divide by 2, one of these operations seems redundant and the result could be wrong.