fix: generator input silently bypasses make_linked_list empty-list contract

[peda-cos]

Describe your change

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: changed together with the code because the doctests are the regression proof for this bug; the new cases fail on the current code.
• 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.
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Description

make_linked_list(elements_list: Iterable[int]) documents that an empty input raises "The Elements List is empty", but the check is a truthiness test if not elements_list. Truthiness of Iterable has no such meaning for arbitrary iterables, so make_linked_list(x for x in []) currently returns an empty LinkedList instead of raising, and a non-empty generator works only by luck.

Materialize the iterable (elements_list = list(elements_list)) before the emptiness check so the documented contract holds for any iterable. The annotation is unchanged.

How I tested

• Before the change: make_linked_list(x for x in range(0)) silently returned an empty LinkedList.
• After the change: raises Exception: The Elements List is empty; make_linked_list(x for x in [7, 25]) still builds 7 -> 25.
• pytest --doctest-modules data_structures/linked_list/print_reverse.py — 7 passed, including the two new generator doctests.