Issue with seq2seq using the TF tutorial

Would you have any ideas on what could be causing this?

```
magnitude = tf.sqrt(tf.reduce_sum(tf.square(dec_memory[1])))
tf.scalar_summary("magnitude at t=1", magnitude)

Truncated Traceback (Use C-c C-x to view full TB):
/usr/local/lib/python2.7/site-packages/tensorflow/python/framework/tensor_shape.pyc in assert_has_rank(self, rank)
596 """
597 if self.ndims not in (None, rank):
--> 598 raise ValueError("Shape %s must have rank %d" % (self, rank))
599
600 def with_rank(self, rank):

ValueError: Shape (?, 100) must have rank 1
```