fix: handle empty input in tim_sort

[pony-maggie]

Describe your change:

Fixed tim_sort([]) so it returns an empty list instead of raising IndexError when the implementation tries to read lst[0].

Why

Sorting an empty sequence should be a valid no-op. Other sort implementations in this repository handle empty input, and Python's sorted([]) returns [].

How tested

• RED: /opt/homebrew/opt/python@3.14/bin/python3.14 -m doctest -v sorts/tim_sort.py failed with IndexError: list index out of range before the fix
• /opt/homebrew/opt/python@3.14/bin/python3.14 -m doctest -v sorts/tim_sort.py
• /tmp/thealgorithms-py314-pytest/bin/python -m pytest --doctest-modules sorts/tim_sort.py -q
• Randomized comparison of tim_sort(case) against sorted(case) for 100 generated lists
• git diff --check

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".