[BugFix][Kernel]: fix illegal memory access in causal_conv1d when conv_states is None

[xffxff]

fix #10895

Issue #10895 reports an illegal memory access error on H100 GPUs when calling the causal_conv1d_fn function with specific input shapes and when conv_states is not provided. After some investigation, I found that the root cause as an attempt to assign a value to a nullptr.

cc @mzusman @tlrmchlsmth

[github-actions]

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[mzusman]

Thanks for fixing the bug! it would be great if you could add a test case to test_causal_conv1d.py for running the causal_conv1d_fn kernel without an initial state

[xffxff]

it would be great if you could add a test case to test_causal_conv1d.py for running the causal_conv1d_fn kernel without an initial state

@mzusman I've added tests for causal_conv1d_fn kernel without an initial state and all the tests passed successfully in my local environment.

[mzusman]

it would be great if you could add a test case to test_causal_conv1d.py for running the causal_conv1d_fn kernel without an initial state

@mzusman I've added tests for causal_conv1d_fn kernel without an initial state and all the tests passed successfully in my local environment.

Thanks! LGTM @tlrmchlsmth

[jeejeelee]

Thank you very much. LGTM, leaving the final decision to @tlrmchlsmth

[tlrmchlsmth]

Thanks for the contribution!