TensorflowでThe last dimension of the inputs to `Dense` should be defined. Found `None`.というエラーが出る

Question

Tensorflow(1.12)でNNの層を作っています。

def _conv1d_block(inputs, filters, keep_prob=0.25, name='conv'):
    with tf.variable_scope(name):
        conv = tf.contrib.layers.conv1d(inputs, filters, kernel_size=2, stride=1, padding='same')
        #conv = tf.contrib.layers.batch_norm(conv, updates_collections=None, decay=0.99, scale=True, center=True)
        conv = tf.layers.max_pooling1d(conv, pool_size=2, strides=2, padding='same')
        conv = tf.nn.dropout(conv, keep_prob=keep_prob)
        return conv
    

def conv1d(x, z_dim, reuse=False):
    with tf.variable_scope('conv1d', reuse=reuse):
        net = _conv1d_block(x, filters=66, keep_prob=0.25, name='conv_1')
        net = _conv1d_block(net, filters=132, keep_prob=0.3, name='conv_2')
        #net = conv_block(net, filters=264, keep_prob=0.5, name='conv_3') 
        net = tf.contrib.layers.flatten(net)
        net = tf.layers.dense(net, 64)
        net = tf.nn.relu(net)
        #net = tf.nn.dropout(net, keep_prob=0.4)
        net = tf.layers.dense(net, z_dim)
        #net = tf.nn.relu(net)
        
        return net


def _conv2d_block(inputs, out_channels, keep_prob=0.5, name='conv'):
    with tf.variable_scope(name):
        conv = tf.layers.conv2d(inputs, out_channels, kernel_size=2, padding='SAME')
        #conv = tf.contrib.layers.batch_norm(conv, updates_collections=None, decay=0.99, scale=True, center=True)
        conv = tf.nn.relu(conv)
        conv = tf.contrib.layers.max_pool2d(conv, 2)
        conv = tf.nn.dropout(conv, keep_prob=keep_prob)
        return conv


def conv2d(x, z_dim, reuse=False):
    with tf.variable_scope('conv2d', reuse=reuse):
        net = _conv2d_block(x, 32, keep_prob=0.25, name='conv_1')
        net = _conv2d_block(net, 64, keep_prob=0.3, name='conv_2')
        net = _conv2d_block(net, 128, keep_prob=0.5, name='conv_3')
        #net = _conv2d_block(net, z_dim, name='conv_4')
        net = tf.contrib.layers.flatten(net)
        net = tf.layers.dense(net, 64)
        net = tf.nn.relu(net)
        #net = tf.nn.dropout(net, keep_prob=0.4)
        net = tf.layers.dense(net, z_dim)
        #net = tf.nn.relu(net)
        return net

このように、conv1dとconv2dでほとんど作りは同じなのに、conv2dのみエラーが出てしまいます。
エラーは以下のように、次元がNoneになっているということです。conv1dでは同じことができているのにconv2dではできないのは、なぜでしょうか？

File "/fewshot/models/nnlib.py", line 51, in conv2d
    net = tf.layers.dense(net, 64)
  File "/anaconda3/envs/tf1_12/lib/python3.6/site-packages/tensorflow/python/layers/core.py", line 184, in dense
    return layer.apply(inputs)
  File "/anaconda3/envs/tf1_12/lib/python3.6/site-packages/tensorflow/python/keras/engine/base_layer.py", line 817, in apply
    return self.__call__(inputs, *args, **kwargs)
  File "/anaconda3/envs/tf1_12/lib/python3.6/site-packages/tensorflow/python/layers/base.py", line 374, in __call__
    outputs = super(Layer, self).__call__(inputs, *args, **kwargs)
  File "/anaconda3/envs/tf1_12/lib/python3.6/site-packages/tensorflow/python/keras/engine/base_layer.py", line 746, in __call__
    self.build(input_shapes)
  File "/anaconda3/envs/tf1_12/lib/python3.6/site-packages/tensorflow/python/keras/layers/core.py", line 933, in build
    raise ValueError('The last dimension of the inputs to `Dense` '
ValueError: The last dimension of the inputs to `Dense` should be defined. Found `None`.

Answer 1

placeholderに入れたデータの型が間違っていたのが原因でした。