Implementing a CNN with one convolution layer
I guess you should change the following line to solve the problem:

model.add(Conv2D(64, strides=5, kernel_size=EMBED_DIM, activation="relu", padding='valid'))


instead use this code:

model.add(Conv2D(64, strides=5, kernel_size=EMBED_DIM, activation="relu", padding='same'))


this will keep the dimension of your input. If it does not work, let me know to help you more.