PYSEC-2026-3342 Missing validation causes denial of service via `Conv3DBackpropFilterV2`

Impact The implementation of tf.rawops.UnsortedSegmentJoin does not fully validate the input arguments. This results in a CHECK-failure which can be used to trigger a denial of service attack: python import tensorflow as tf tf.strings.unsortedsegmentjoin inputs='123', segmentids=0, numsegments=-1...