Fix LeakyRelu behaviour on empty input (#18934)

[bgawrych]

Description

fix #18934

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Comments

In numpy mode everything works fine.
NDArray mode throws:

  File "leaky.py", line 5, in <module>
    b = mx.ndarray.LeakyReLU(input)
  File "<string>", line 72, in LeakyReLU
  File "/home/wihajster/Desktop/incubator-mxnet/python/mxnet/_ctypes/ndarray.py", line 82, in _imperative_invoke
    check_call(_LIB.MXImperativeInvokeEx(
  File "/home/wihajster/Desktop/incubator-mxnet/python/mxnet/base.py", line 246, in check_call
    raise get_last_ffi_error()
mxnet.base.MXNetError: Traceback (most recent call last):
  File "../src/imperative/imperative.cc", line 678
MXNetError: Check failed: shape_is_known(arr.shape()):

I think this is correct behavior, as legacy mode doesn’t let empty arrays.

[mxnet-bot]

Hey @bgawrych , Thanks for submitting the PR
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[szha]

thanks for the fix! @bgawrych