Add test for LZString methods with None input

[noobforvictory]

Hey there,

I'm thrilled to start contributing to the project! As a newcomer to open source, I'm focusing on writing unit tests to understand the code base. Any feedback or guidance is appreciated.

[cla-bot]

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[eyurtsev]

Hi @noobforvictory thanks for the contribution! It's better to focus on an existing issue rather than writing unit tests for existing.

I'd suggest starting with langchain-community (in the main langchain-repo) if you're getting started with python or looking for simple issues to contribute with.