Check for emptiness of case.split function input

[krysal]

Fixes

Fixes #3984 by @krysal

Description

I don't know how to reproduce the issue but I think this small PR should fix it.

Testing Instructions

–.

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[dhruvkb]

Approving, provided @obulat's comment is addressed.

[obulat]

Thank you for fixing a long-lingering issue ✨