Prevent division by 0 in OneHot implementation

If input indices is degenerate, the implementation would do a divide by zero. See https://github.com/tensorflow/tensorflow/blob/745d57df6d5e9bc568666a2a48ed8dd629c27241/tensorflow/lite/kernels/one_hot.cc#L68-L72

PiperOrigin-RevId: 370966870
Change-Id: Ie018337811c8016b5a1d3a277d00d5f2e19a2058