ValueError: destinations can not be empty

This error happen when I try to : get output from the layer before last layer as features, and try to compute loss with an expected features, then propagate and update the input (not the network’s weight, but the input) using cosine similarity loss. I cannot find any clue about this bug. Is there anyone meet this problem before?

Sample working code which computes intermediate layer output and cosine similarity loss

import tensorflow as tf
(x_train, y_train), (x_test, y_test)=tf.keras.datasets.mnist.load_data()
model = tf.keras.Sequential([
tf.keras.layers.Dense(10, activation=“softmax”)
intermediate_layer = tf.keras.Model(inputs=model.inputs,
outputs=model.outputs + [model.layers[1].output])
cosine_loss = tf.keras.losses.CosineSimilarity()
optimezer = tf.optimizers.Adam()
with tf.GradientTape() as tape:
y_pred, intermediate_output= intermediate_layer(x_train)
loss = cosine_loss(tf.one_hot(y_train, 10), y_pred)
gradients = tape.gradient(loss, intermediate_layer.variables)


[[1.2817659e+02 0.0000000e+00 2.1529781e+01 … 1.4793573e+02
1.7081753e+01 0.0000000e+00]
[3.1562555e+02 0.0000000e+00 8.2275620e+01 … 0.0000000e+00
0.0000000e+00 0.0000000e+00]
[1.5004303e+01 5.3053143e+01 0.0000000e+00 … 0.0000000e+00
0.0000000e+00 9.4606926e+01]

[0.0000000e+00 0.0000000e+00 1.2034170e+02 … 1.3093190e+02
0.0000000e+00 1.5922928e-01]
[2.4972404e+02 0.0000000e+00 2.2767758e+02 … 0.0000000e+00
0.0000000e+00 2.0227030e+01]
[9.6311852e+01 0.0000000e+00 0.0000000e+00 … 5.8486767e+00
0.0000000e+00 9.8323425e+01]], shape=(60000, 64), dtype=float32)